How Many A4 Sheets Fit in Standard-Size Mail? Tri-Fold Counts for Nagagata 3 and 40, and the 50 g Limit

What qualifies for teikei (standard-size) mail at ¥110

Teikei mail is the cheapest way to send a letter in Japan. Since the rate revision in October 2024 it costs a flat ¥110 up to 50 g (still the same as of October 2026). Previously there were separate rates for up to 25 g and up to 50 g, but now there's only one step, so the only thing to watch is whether you go over 50 g.

The maximum size of 12 × 23.5 cm is exactly the size of a Nagagata 3 envelope. In other words, any envelope larger than a Nagagata 3 is never teikei, even with a single sheet inside. Conversely, an envelope of Nagagata 3 size or smaller switches to the teikeigai (non-standard) within-limits rate as soon as it exceeds either 50 g or 1 cm in thickness.

One sheet of A4 copy paper weighs about 4 g (how to work it out)

Paper weight is defined by its grammage, the weight per square meter (g/m²). Typical office copy paper is around 64 g/m². A4 is 210 × 297 mm, so its area is 0.21 × 0.297 = about 0.0624 m². Multiply that by the grammage and you get the weight of one sheet.

1. 1

   Find the area

   A4: 0.21 m × 0.297 m = 0.0624 m². For B5, 0.182 × 0.257 = 0.0468 m².

2. 2

   Multiply by the grammage

   For copy paper (64 g/m²), 0.0624 × 64 ≈ 3.99 g. Remembering it as roughly 4 g is good enough.

3. 3

   Add the envelope

   A kraft Nagagata 3 envelope weighs about 5 g. With 11 A4 sheets, 5 + 3.99 × 11 ≈ 48.9 g, which stays under 50 g.

Paper packaging and catalogs in Japan sometimes show a ream weight such as "55 kg" or "70 kg". This is a different measure, and roughly 55 kg ≈ 64 g/m², 70 kg ≈ 81.4 g/m² and 90 kg ≈ 104.7 g/m². The paper in an office printer is almost always copy paper, so when in doubt, calculate with 4 g per sheet.

How many sheets each envelope carries for ¥110

These counts come from the envelope weight (about 5 g for Nagagata 3 and Yō-nagagata 3, about 4 g for Nagagata 40 and Nagagata 4) and the weight of one sheet, keeping the total within 50 g. Thickness is estimated as sheet thickness × number of sheets × layers from folding, but in every combination weight hits its limit first, with room to spare before 1 cm.

Nagagata 40 is 1 g lighter than Nagagata 3, so with thick paper it takes one more sheet. Nagagata 4 is an envelope for B5. A4 tri-folded is still 9.9 cm wide, and won't fit in a Nagagata 4, whose inside width is only about 8.6 cm. To send A4 in a small envelope, use Nagagata 40 folded in four or Nagagata 3 folded in three.

Counting a return envelope and cover letter

In practice, you'll often include a cover letter or return envelope with the documents. Count a cover letter as one sheet of A4, and add one envelope's weight for a return envelope (about 5 g for Nagagata 3). The stamp on a return envelope weighs almost nothing, so you can ignore it.

• Nagagata 3 + 1 cover letter + documents: up to 10 sheets of documents for ¥110 (11 sheets in total)
• Nagagata 3 + Nagagata 3 return envelope + 1 cover letter + documents: up to 9 sheets of documents for ¥110 (5 + 5 + 3.99 × 10 ≈ 49.9 g)
• Two copies of a document on thick paper (such as a contract) plus a cover letter on copy paper: 5 + 5.08 × 2 × 2 + 3.99 ≈ 29.3 g. Two copies of two sheets each for signing leave plenty of room
• An A4 clear file weighs about 20 g and won't fit in a Nagagata 3 anyway. If you want to use one, switch to Kaku 2

Take care when the calculation lands right at the limit, like 49.9 g in the second example. The envelope's paper thickness, printing ink, glue and tape can all shift the weight by around 1 g. If you're within 3 g of the limit, it's safer to remove a sheet and split it into two letters, or put ¥180 of stamps on from the start. If it comes back for insufficient postage, delivery is delayed by several days.

When do you hit 1 cm in thickness?

A sheet of copy paper is about 0.09 mm thick. Tri-folded, three layers stack up, so each sheet adds about 0.27 mm. Even 11 sheets come to about 3 mm, nowhere near 1 cm. With paper alone, you can assume the weight limit of teikei mail comes first.

Thickness matters when you include something other than paper. A small booklet, a card-type membership card, a key or USB stick, or a small item wrapped in bubble wrap can easily exceed 1 cm even when light, and then the teikeigai within-limits rate applies even under 50 g. Post office counters have a special ruler for measuring thickness. To check it yourself, stand a ruler up on a flat desk and measure the thickest point.

Checking without scales

A kitchen scale measures in 1 g steps, but many people don't have one. In that case, these methods give you a rough idea.

1. 1

   Calculate from the number of sheets

   As in the tables above, estimate envelope weight + weight of one sheet × number of sheets. In the Postage Calculator, just choose the envelope type and the number and folding of sheets to see the weight, the postage and how many more sheets until the next rate.

2. 2

   Compare with 1-yen coins

   A 1-yen coin weighs exactly 1 g. Use a ruler as a lever with the envelope on one side and 50 one-yen coins on the other, and the way it tips tells you roughly whether you're over 50 g.

3. 3

   Have it weighed at a post office counter

   This is the surest way. If you pay at the counter, you don't need to put stamps on, and there's no risk of underpaying.

If you drop it in a postbox, you have to judge yourself whether the postage is enough. Above about 45 g in particular, the real thing being heavier than your calculation can easily push it past 50 g, so take it to a counter or pay a rate with some margin.

Options when you're about to go over 50 g

When your documents reach 12 sheets or more and won't fit in teikei mail, there are three main options. Comparing on price alone, sending them unfolded in a Kaku 2 often turns out to cost you nothing extra.

For 12 to 21 sheets, tri-folding into a Nagagata 3 or putting them unfolded into a Kaku 2 both cost ¥180. In that case the Kaku 2, which saves folding, is easier for the recipient to read, scan and file. Splitting into two letters costs ¥110 × 2 = ¥220, which is actually more expensive, and the recipient has to match up the two. On the other hand, using a Kaku 2 for 11 sheets or fewer costs ¥140, ¥30 more, so for thin documents a Nagagata 3 is enough.

Related reading

• Sending A4 unfolded: How much postage for a Kaku 2 envelope? How many A4 sheets for ¥140 and ¥180
• Categories for large or thick envelopes: Teikeigai within limits vs oversize
• Using up ¥84 stamps you have at home: How much to add to an ¥84 stamp? Making up old-rate stamps
• Adding tracking or a delivery record: Tokutei Kiroku, Kan'i Kakitome or Letter Pack: which is cheapest?

FAQ

How many sheets of A4 copy paper can I send for ¥110?

Tri-folded into a Nagagata 3 envelope (about 5 g), up to 11 sheets (about 48.9 g) go as ¥110 teikei mail. From 12 to 23 sheets it becomes teikeigai within limits, up to 100 g, at ¥180.

How much does one sheet of A4 copy paper weigh?

About 4.0 g for standard copy paper (64 g/m²). Multiply the A4 area of 0.0624 m² by the grammage. Thick paper (81.4 g/m²) is about 5.1 g and extra-thick (104.7 g/m²) about 6.5 g.

What postage do I need if a Nagagata 3 envelope goes over 50 g?

¥180, the teikeigai within-limits rate for up to 100 g. The teikeigai up-to-50 g rate of ¥140 is for envelopes larger than standard size, so a 51 g Nagagata 3 costs ¥180.

How many sheets can I send for ¥110 with a return envelope?

With a Nagagata 3 return envelope inside a Nagagata 3, 10 sheets of copy paper in total (including the cover letter) come to about 49.9 g. That's right at the limit, so remove a sheet or use ¥180 of stamps to be safe.

Does A4 fit in a Nagagata 4 envelope?

No. Tri-folded A4 is 9.9 × 21 cm, wider than a Nagagata 4 (9 × 20.5 cm). To send A4 folded small, use Nagagata 40 folded in four or Nagagata 3 folded in three.