Paper types and weightPS-12
What are the units of paper thickness? Grammage, ream weight and caliper (mm) compared and converted, typical copy paper, Kent paper and postcard thickness, and what printers can feed
Paper thickness is expressed in three units: grammage, ream weight and caliper. We show how they differ and convert in tables, then go through common papers and printer limits, step by step.
In this article (14 sections)
- Conclusion: which unit expresses paper thickness, and how thick is typical paper?
- How do you convert paper thickness with the calculator?
How do the units of paper thickness differ?3
How do you convert paper thickness between ream weight and grammage?1
How thick are copy paper, Kent paper, drawing paper and postcards?3
- What do caliper and grammage tell you about paper thickness?
- How many mm thick are 100 or 500 sheets of paper?
How thick a paper can a printer feed?1
How do you choose paper thickness by use?1
- What are the common mistakes with paper thickness?
- What terms come up with paper thickness?
What else should you know along with paper thickness?3
- Sources
Paper thickness cannot be pinned down by a single number. In paper shops and print orders, thickness is often given in units of weight.
The units of paper thickness are grammage, ream weight and caliper. Grammage and ream weight are weights. Only caliper is the actual thickness.
Here is the key point. Compare paper thickness only after converting it to grammage (g/m²).
This article covers the following:
- How grammage, ream weight and caliper differ, and how to read the units
- Converting between shiroku-ban and kiku-ban ream weight and grammage (formulas and tables)
- Typical thickness of copy paper, Kent paper, drawing paper and postcards
- How tightly packed a paper is (density), worked out from caliper and grammage
- How thick 100 and 500 sheets are when stacked
- How thick a paper home inkjet printers and laser printers can feed
- How paper thickness relates to mailing weight
Values are shown in tables based on JIS, manufacturers' published figures and Japan Post's terms and conditions.
Conclusion: which unit expresses paper thickness, and how thick is typical paper?
| Paper | Grammage (g/m²) | Shiroku-ban ream (kg) | Caliper (published) (mm) | Typical use |
|---|---|---|---|---|
| Shiroku-ban 45 kg equivalent | 52.3 | 45 | Newspaper inserts | |
| Copy paper (FUJIFILM BI "EP") | 65 | 55.9 | 0.091 | Copiers and printers |
| Recycled copy paper (FUJIFILM BI "SG") | 67 | 57.6 | 0.093 | Copiers and printers (50% recycled pulp) |
| Shiroku-ban 70 kg equivalent | 81.4 | 70 | Leaflets, flyers, magazine text pages | |
| Shiroku-ban 90 kg equivalent | 104.7 | 90 | Leaflets, posters | |
| Shiroku-ban 110 kg equivalent | 127.9 | 110 | Tickets, weekly magazine covers, brochures | |
| Minimum for a private postcard (2 g), computed | 135.1 | 116.1 | Postcards (2–6 g ÷ 0.0148 m²) | |
| Shiroku-ban 135 kg equivalent | 157 | 135 | Fashion magazine covers, business cards, company brochures | |
| Kent paper (KOKUYO, 157 g) | 157 | 135 | 0.19 | Ink, pencil, paint; wet stretching |
| Drawing paper (KOKUYO Campus sketchbook) | 157 | 135 | Sketchbooks | |
| Shiroku-ban 180 kg equivalent | 209.3 | 179.9 | Fashion magazine covers, business cards, postcards | |
| Kent paper (KOKUYO, 230 g) | 230 | 197.7 | 0.26 | Ink, pencil, paint; model making |
Source (7)
- FUJIFILM Business Innovation, "Paper thickness" (grammage and typical uses)
- FUJIFILM Business Innovation, "EP" (65 g/m², 91 μm)
- FUJIFILM Business Innovation, "SG" (67 g/m², 93 μm)
- Computed from Japan Post Domestic Postal Terms, Art. 22 (private postcards 2–6 g)
- KOKUYO Kent paper A4 157 g, SE-KP19 (157 g/m², 0.19 mm)
- KOKUYO Campus sketchbook A4-S, E-300 (drawing paper, 157 g/m²)
- KOKUYO Kent paper A4 230 g, SE-KP39 (230 g/m², 0.26 mm)
Typical paper thicknesses are shown in the table above. Each row lists the grammage, the shiroku-ban ream weight and the caliper.
The ream weights in the table are calculated from the grammage. Caliper is filled in only for products whose manufacturer publishes it.
Even at the same grammage, caliper varies with the type of paper. When you need the caliper, check the label from the maker of the paper you are buying.
If in doubt, compare by the grammage (g/m²) figure. Ream weight changes with the size of the full sheet, so it is easy to mix up.
How do you convert paper thickness with the calculator?
You can convert paper thickness with "Paper weight conversion" in the tool above. Enter the grammage to get the shiroku-ban and kiku-ban ream weights.
The tool runs entirely in your browser and does not send the values you enter. The formulas are as follows, the same calculation as the tables.
- Shiroku-ban ream weight (kg) = grammage × 0.8597
- Kiku-ban ream weight (kg) = grammage × 0.5972
- Grammage (g/m²) = shiroku-ban ream weight ÷ 0.8597
The same formulas work in reverse. For example, shiroku-ban 90 kg is 90 ÷ 0.8597 ≈ 104.7 g/m².
How do the units of paper thickness differ?
The units of paper thickness are grammage, ream weight and caliper. Grammage and ream weight are units of weight, and caliper is a unit of length.
| Unit | Japanese name and reading | What it shows | Where you often see it |
|---|---|---|---|
| Grammage (g/m²) | tsuboryo (坪量) | Weight of 1 m² of paper | Copy paper packaging, printer manuals |
| Ream weight (kg) | renryo (連量) | Weight of 1,000 sheets of a set size | Print shop and paper store guides |
| Caliper (mm, μm) | μm is read "micrometer" | Actual thickness of one sheet | Product spec sheets |
Of the three, grammage is the one that lets you compare papers directly. Ream weight cannot be compared unless the sheet size (the size of the full sheet) is the same.
What is grammage (g/m²)?
Grammage is the weight of 1 m² of paper in grams. In Japanese it is also called beitsubo (米坪), from "weight per square meter."
Heavier paper tends to be thicker, so grammage is used as a guide to thickness. FUJIFILM Business Innovation (FUJIFILM BI, a maker of multifunction printers) gives the same explanation.
Paper changes weight with humidity. So it is weighed under standard conditions of 23°C and 50% humidity. This is an ISO (International Organization for Standardization) rule.
Copy paper and printer manuals state grammage.
What is ream weight (kg)?
Ream weight is the weight in kilograms of 1,000 sheets (one ream) of paper of a set size. For paperboard (thick board), one ream is 100 sheets.
Ream weight changes with the sheet size it is measured at. For the same paper, the larger the sheet, the larger the ream weight.
When a Japanese print shop says "70kg" or "90kg", it is often a shiroku-ban ream weight. When comparing ream weights, first check which sheet size they refer to.
Some stores write the same thing as kinryo (斤量).
What is caliper (mm, μm)?
Caliper is the thickness of one sheet expressed as a length. The unit is mm or μm, and 1 mm is 1,000 μm.
In FUJIFILM BI's example, 0.088 mm is written as "88μm". It is also sometimes written "88μ (micron)", leaving out the m.
Caliper varies with the type of paper even at the same grammage. The more tightly packed the paper, the thinner it is at the same grammage.
How do you convert paper thickness between ream weight and grammage?
Converting paper thickness uses the area of the full sheet (the large sheet before cutting). Ream weight (kg) comes from grammage × area of one full sheet (m²).
| Full sheet size | Dimensions (mm) | Area (m²) | Ream weight = grammage × |
|---|---|---|---|
| Shiroku-ban | 788 × 1091 | 0.8597 | 0.8597 |
| Kiku-ban | 636 × 939 | 0.5972 | 0.5972 |
| A-series full sheet (A-ban) | 625 × 880 | 0.5500 | 0.55 |
| B-series full sheet (B-ban) | 765 × 1085 | 0.8300 | 0.83 |
The full sheet dimensions are the values in JIS P 0202 (base sheet sizes of paper). The areas were found by multiplying the dimensions.
The shiroku-ban calculation goes like this:
- Area: 0.788 × 1.091 ≈ 0.8597 m²
- Weight of 1,000 sheets: grammage × 0.8597 × 1,000 (g)
- Convert to kg: the value above ÷ 1,000 = grammage × 0.8597 (kg)
The 1,000 sheets and the 1,000 for converting g to kg cancel each other out. That is why the formula needs only one multiplication.
How much do shiroku-ban and kiku-ban ream weights differ?
| Paper | Grammage (g/m²) | Shiroku-ban ream (kg) | Kiku-ban ream (kg) | A-ban ream (kg) |
|---|---|---|---|---|
| Shiroku-ban 45 kg equivalent | 52.3 | 45 | 31.2 | 28.8 |
| Shiroku-ban 70 kg equivalent | 81.4 | 70 | 48.6 | 44.8 |
| Shiroku-ban 90 kg equivalent | 104.7 | 90 | 62.5 | 57.6 |
| Shiroku-ban 110 kg equivalent | 127.9 | 110 | 76.4 | 70.3 |
| Shiroku-ban 135 kg equivalent | 157 | 135 | 93.8 | 86.4 |
| Shiroku-ban 180 kg equivalent | 209.3 | 179.9 | 125 | 115.1 |
Source: FUJIFILM Business Innovation, "Paper thickness" (grammage and typical uses)
As the table shows, the kiku-ban ream weight is about 0.69 times the shiroku-ban one. That is because 0.5972 ÷ 0.8597 ≈ 0.695.
For example, paper that is 90 kg in shiroku-ban is 62.5 kg in kiku-ban. Mix up the sheet sizes, and you misjudge the thickness by one grade or more.
If a paper is listed only as "90kg", ask whether that is shiroku-ban or kiku-ban. That alone prevents a thickness mix-up.
How thick are copy paper, Kent paper, drawing paper and postcards?
Typical thicknesses of commonly used papers are shown in the table below. They come from manufacturers' published figures and from calculations based on postal rules.
| Paper | Grammage (g/m²) | Caliper (mm) | Source |
|---|---|---|---|
| Copy paper (typical) | 64 to 68 | Not published | FUJIFILM BI explainer |
| Copy paper "EP" | 65 | 0.091 | FUJIFILM BI |
| Recycled copy paper "SG" | 67 | 0.093 | FUJIFILM BI |
| Plain paper range for inkjet | 64 to 90 | 0.08 to 0.11 | Epson manual |
| Kent paper (KOKUYO premium Kent paper) | 157, 210, 230, 262 | 0.19 (157 g), 0.26 (230 g) | KOKUYO |
| Drawing paper (KOKUYO Campus sketchbook) | 157 | Not published | KOKUYO |
| Private postcard | About 135 to 405 (calculated) | No rule | Calculated from Japan Post's terms |
How many mm thick is copy paper?
Copy paper is about 0.09 mm thick. FUJIFILM BI's "EP" is 0.091 mm, and "SG" is 0.093 mm.
FUJIFILM BI's explainer gives 64 to 68 g/m² as typical for copy paper. As a shiroku-ban ream weight, that is about 55 to 58 kg.
In shiroku-ban ream weight, copy paper is a thin paper of around 55 kg. It is a little thinner than the 70 kg paper used by print shops.
How thick are Kent paper and drawing paper?
Kent paper and drawing paper have more than twice the grammage of copy paper. KOKUYO makes both in 157 g/m².
KOKUYO's premium Kent paper comes in four weights: 157, 210, 230 and 262 g/m². Its published caliper is 0.19 mm at 157 g/m² and 0.26 mm at 230 g/m².
Kent paper is more tightly packed than copy paper, so it is thin for its grammage. The calculation is shown in the density section below.
The caliper (mm) of drawing paper is not listed on KOKUYO's product page. Compare drawing paper by grammage. Drawing paper sizes are covered in Drawing paper sizes.
How thick is a postcard?
Under Japanese postal rules, a postcard is defined by weight. A private postcard weighs 2 to 6 g, which is about 135 to 405 g/m² in grammage.
A postcard's area is 0.1 × 0.148 = 0.0148 m². The figures come from 2 ÷ 0.0148 ≈ 135 and 6 ÷ 0.0148 ≈ 405.
Copy paper cut to size does not reach the 2 g a postcard needs. For details, see Postcard size.
What do caliper and grammage tell you about paper thickness?
With both caliper and grammage, you can work out how tightly packed a paper is (its density). Density is grammage ÷ caliper.
| Paper | Grammage (g/m²) | Caliper (μm) | Density (g/cm³) |
|---|---|---|---|
| Copy paper "EP" | 65 | 91 | 0.71 |
| Recycled paper "SG" | 67 | 93 | 0.72 |
| Kent paper 157 g | 157 | 190 | 0.83 |
| Kent paper 230 g | 230 | 260 | 0.88 |
The calculation is just grammage (g/m²) divided by caliper (μm). The result comes out directly in g/cm³.
- EP: 65 ÷ 91 ≈ 0.71
- Kent paper 157 g: 157 ÷ 190 ≈ 0.83
Kent paper is about 1.2 times as tightly packed as copy paper. That is why, with more than twice the grammage, its caliper is still only about twice as thick.
If you know the caliper, you can also estimate grammage = caliper × density. But density differs from paper to paper, so treat the result as a rough guide.
How many mm thick are 100 or 500 sheets of paper?
You can estimate the height of a stack as caliper × number of sheets. For EP (0.091 mm), 100 sheets are about 9 mm and 500 sheets about 46 mm.
| Paper | Caliper (mm) | 100 sheets | 500 sheets |
|---|---|---|---|
| Copy paper "EP" | 0.091 | About 9.1 mm | About 45.5 mm |
| Recycled paper "SG" | 0.093 | About 9.3 mm | About 46.5 mm |
| Kent paper 157 g | 0.19 | About 19 mm | About 95 mm |
| Kent paper 230 g | 0.26 | About 26 mm | About 130 mm |
In a real stack, small gaps form between the sheets. When choosing the size of a box or file, leave a little more room than the calculation.
Printer trays also have a limit on how many sheets they can hold. Canon's manuals have an item called "maximum paper loading capacity."
How thick a paper can a printer feed?
The paper thickness a printer can feed is given in its manual as grammage. In Canon's example, inkjet plain paper is 64 to 105 g/m².
| Printer (example) | Type | Usable grammage | As shiroku-ban ream weight |
|---|---|---|---|
| Canon PIXUS TS8330 | Inkjet | Plain paper 64 to 105 g/m² | About 55 to 90 kg |
| Canon PIXUS MG7500 (special paper other than genuine Canon paper) | Inkjet | Up to 200 g/m² | Up to about 172 kg |
| Epson WF-845 (US manual) | Inkjet | Plain paper 64 to 90 g/m² (0.08 to 0.11 mm) | About 55 to 77 kg |
| Canon Satera LBP162 | Laser | 60 to 163 g/m² | About 52 to 140 kg |
The table shows values from the manufacturers' manuals. The shiroku-ban ream weights were calculated as grammage × 0.8597.
For the models above, the rough guide is shiroku-ban 70 to 90 kg for inkjet and up to 135 kg for laser. It varies by model, so always check "supported paper" in the manual.
Canon names paper outside the range as a cause of paper jams in its inkjets. When printing smaller than A5, you also cannot use plain paper cut down to size.
What settings do you use to print thick paper on a laser printer?
For thick paper, match the printer's "paper type" setting to the grammage. On the LBP162, choose the following setting for each grammage.
| Grammage (g/m²) | LBP162 paper type | Automatic 2-sided printing |
|---|---|---|
| 60 | Plain L2 | Yes |
| 61 to 70 | Plain L | Yes |
| 71 to 89 | Plain | Yes |
| 90 to 105 | Heavy 1 | Yes |
| 106 to 120 | Heavy 2 | No |
| 121 to 163 | Heavy 3 (Heavy 4 if print is faint) | No |
Paper at Heavy 2 or thicker cannot be printed with automatic 2-sided printing. Even 2-sided printing works only with set sizes such as A4.
If the setting does not match, the toner (powder ink) may not stick to the paper well enough, and print can come out faint. This is a caution in Canon's manual.
For thick paper, do a test print of just one sheet first. Epson also recommends testing before printing in bulk.
How do you choose paper thickness by use?
Choose paper thickness by working back from what you are making. Typical uses for each grammage, from FUJIFILM BI's explainer, are as follows.
| Paper | Grammage (g/m²) | Shiroku-ban ream (kg) | Typical use |
|---|---|---|---|
| Shiroku-ban 45 kg equivalent | 52.3 | 45 | Newspaper inserts |
| Shiroku-ban 70 kg equivalent | 81.4 | 70 | Leaflets, flyers, magazine text pages |
| Shiroku-ban 90 kg equivalent | 104.7 | 90 | Leaflets, posters |
| Shiroku-ban 110 kg equivalent | 127.9 | 110 | Tickets, weekly magazine covers, brochures |
| Shiroku-ban 135 kg equivalent | 157 | 135 | Fashion magazine covers, business cards, company brochures |
| Shiroku-ban 180 kg equivalent | 209.3 | 179.9 | Fashion magazine covers, business cards, postcards |
Source: FUJIFILM Business Innovation, "Paper thickness" (grammage and typical uses)
Business card thickness is easy to get stuck on. FUJIFILM BI says cards that are too thin do not hold up when kept, and cards that are too thick do not fit in a card case.
How does paper thickness change mailing weight?
As paper gets thicker, mailing weight goes up too. The weight of one A4 sheet can be calculated as grammage × 0.0624.
The area of A4 is 0.21 × 0.297 ≈ 0.0624 m². Standard-size mail in Japan goes up to 50 g, so we worked out how many sheets of paper alone reach that.
| Grammage (g/m²) | Weight of one A4 sheet (calculated) | Sheets of paper alone to reach 50 g |
|---|---|---|
| 65 | About 4.1 g | 12 sheets |
| 81.4 | About 5.1 g | 9 sheets |
| 104.7 | About 6.5 g | 7 sheets |
| 157 | About 9.8 g | 5 sheets |
In practice you also add the weight of the envelope, so fewer sheets fit than the table shows. Check the size and weight limits for standard-size mail on Japan Post's rate table.
How to choose an envelope size is covered in Envelope sizes.
What are the common mistakes with paper thickness?
The most common is comparing ream weights from different sheet sizes. The mistakes people most often ask about are shown in the table below.
| Mistake | What happens | How to fix it |
|---|---|---|
| Comparing shiroku-ban and kiku-ban ream weights | You misjudge the thickness by one grade or more | Convert to grammage before comparing |
| Treating grammage and caliper as the same thing | Same g/m², but a different thickness | Check the caliper on the manufacturer's label |
| Putting thick paper into an inkjet | It can cause paper jams | Check the grammage range in the manual |
| Printing thick paper on the "Plain" setting | The toner can come out faint | Use the "Heavy" setting that matches the grammage |
| Cutting copy paper to make postcards | It falls short of 2 g and does not count as a postcard | Use paper of about 135 g/m² or more |
| Choosing a box at exactly caliper × number of sheets | The gaps mean the paper does not fit | Leave a little room |
When you see a number, first check "which unit" and "which sheet size." These two checks prevent most mix-ups.
What terms come up with paper thickness?
| Term | Meaning | Source |
|---|---|---|
| Grammage, beitsubo (米坪) | Weight of 1 m² of paper (g/m²) | FUJIFILM BI |
| Ream | A bundle of 1,000 sheets. 100 sheets for paperboard | FUJIFILM BI |
| Ream weight | Weight of one ream at a set sheet size (kg) | FUJIFILM BI |
| Caliper | Thickness of one sheet (mm, μm) | FUJIFILM BI |
| Full sheet | The large sheet before cutting | JIS P 0202 |
| Shiroku-ban, kiku-ban | Names of full sheet sizes | JIS P 0202 |
| Standard conditions | 23°C and 50% humidity. The conditions for weighing paper | FUJIFILM BI (ISO) |
| Density | Grammage ÷ caliper. How tightly packed a paper is | Calculated in this article |
| Paperboard | Thick board used for corrugated boxes and cartons | Japan Paper Association |
| Heavy 1 to 4 | Paper type settings on a laser printer | Canon manual |
What else should you know along with paper thickness?
Does the type of paper change how thick it feels?
Yes. Even at the same grammage, caliper and feel change with the type of paper.
The features of each paper type and how to choose one are covered in Types of paper.
What are the thickness rules for postcards and envelopes?
Postcards are defined by weight, and standard-size mail has a thickness limit of 1 cm.
Check the postcard rules in Postcard size and envelopes in Envelope sizes.
Where do the numbers on this site come from?
The grammage and ream weight tables on this site all come from a single dataset. The tables and the tool use the same formulas.
How we check figures and our editorial policy are described in About this site.
Paper types and weightWhat types of paper are there? Woodfree, coated, Kent, drawing paper and washi compared, how to choose by use, and which work with inkjet and laser printersTypes of paper: paper vs paperboard, Western vs washi, coated vs uncoated, woodfree, art, matte, Kent, drawing, kraft and recycled paper, choosing by use, and printers.
Envelopes and mailWhat Size Is a Japanese Postcard in cm? Pixels, Aspect Ratio, Japan Post Rules and Making Your OwnJapanese postcard size in cm and pixels by dpi, vs A6 and L-size, aspect ratio, Japan Post rules for return and private postcards, bleed, A4 layout and overseas cards.
Envelopes and mailWhat Are the Envelope Sizes in Japan? Nagagata, Kakugata and Yogata Dimensions, What Paper Fits, Kaku 2 vs Kaku A4, and Japan Post Mail ClassesJapanese envelope sizes (Nagagata, Kakugata, Yogata) with what fits: A4 and B5 folds and clearance, Kaku 2 vs Kaku A4, Japan Post mail classes and sheets per 50 g.What are common questions about paper thickness?
What are the units of paper thickness?
There are three: grammage (g/m²), ream weight (kg) and caliper (mm).
When comparing, convert to grammage.
How many mm thick is copy paper?
About 0.09 mm. FUJIFILM BI's EP is 0.091 mm, and SG is 0.093 mm.
100 sheets are about 9 mm, and 500 sheets about 46 mm.
How many g/m² is 90 kg paper?
Shiroku-ban 90 kg is about 104.7 g/m². Kiku-ban 90 kg is about 150.7 g/m².
The answer depends on the sheet size, so check which one is meant.
How thick is 135 kg paper?
Shiroku-ban 135 kg is about 157 g/m². KOKUYO's 157 g/m² Kent paper is 0.19 mm.
Caliper varies with the type of paper, so check the product label.
Can a home printer print on thick paper?
It depends on the model. On Canon's MG7500, special paper other than genuine Canon paper goes up to 200 g/m².
Check the grammage in the "supported paper" section of the manual.
How do you convert μm to mm?
1 mm = 1,000 μm. 0.09 mm is 90 μm.
Divide the μm figure by 1,000 to get mm.
Sources
- Paper thickness (FUJIFILM Business Innovation, in Japanese. Grammage, ream weight, caliper and typical uses)
- Paper basics, common conventions: weight (FUJIFILM Business Innovation, in Japanese. Ream, ream weight and standard conditions)
- EP copy/printer paper (FUJIFILM Business Innovation, in Japanese. 65 g/m², 0.091 mm)
- SG recycled copy/printer paper (FUJIFILM Business Innovation, in Japanese. 67 g/m², 0.093 mm)
- Premium Kent paper A4 157 g, SE-KP19 (KOKUYO, in Japanese. 157 g/m², 0.19 mm)
- Premium Kent paper A4 230 g, SE-KP39 (KOKUYO, in Japanese. 230 g/m², 0.26 mm)
- Campus sketchbook for general and student use A4-S, E-300 (KOKUYO, in Japanese. Drawing paper, 157 g/m²)
- PIXUS TS8330 series: supported paper (Canon, in Japanese. Plain paper 64 to 105 g/m²)
- PIXUS TS8330 series: paper that cannot be used (Canon, in Japanese. Paper outside the range)
- PIXUS MG7500 series: supported paper (Canon, in Japanese. Special paper up to 200 g/m²)
- Satera LBP162/LBP161: paper (Canon, in Japanese. 60 to 163 g/m² and paper type settings)
- WF-845 Paper Specifications (Epson, US)
- Domestic Postal Terms and Conditions, Article 22 (Japan Post, in Japanese. Private postcards weigh 2 to 6 g)
- Domestic rates: letters and postcards (Japan Post, in Japanese. Size and weight of standard-size mail)
- Types of paper (Japan Paper Association, in Japanese. Paperboard)
- JIS P 0202 Base sheet sizes of paper, JIS P 8124 Grammage measurement method (Japanese Industrial Standards Committee, JIS search; in Japanese. Full sheet dimensions and grammage)