Teikeigai Within Limits vs Oversize: Size, the 3 cm Thickness Rule, Weight and the Rate Table

Decide in the order teikei → within limits → oversize → not mailable

For letters and envelopes, check whether each category applies starting from the smallest, and you won't get confused. If even one of size, thickness or weight exceeds the limit, move to the next category.

Only the oversize condition uses the idea of a three-side total. If the long side is within 60 cm and length, width and thickness add up to 90 cm or less, it can go as oversize. For example, a 40 × 30 × 10 cm box totals 80 cm and can go as oversize, but 50 × 35 × 10 cm totals 95 cm and can't be sent as mail, so you'd use a parcel service such as Yu-Pack.

Within-limits and oversize rates and the difference (October 2024 revision)

These are the rates revised on October 1, 2024. The October 2026 revision covered services such as Yu-Pack and Click Post, and teikeigai rates did not change. Weight bands are inclusive, so exactly 50 g takes the up-to-50 g rate.

The difference is ¥110 to ¥130 for light items and ¥150 to ¥170 above 500 g. Within limits only goes up to 1 kg, so even if the size is within limits, anything over 1 kg takes the oversize up-to-2 kg rate (¥1,350). For reference, teikei mail costs ¥110 up to 50 g, and a standard-size envelope over 50 g takes the within-limits up-to-100 g rate of ¥180.

Category by envelope type

Here's which category common envelopes fall into with just one sheet of paper inside. As weight or thickness increases, they move up from here.

Kaku 1 and Kaku 0 only go slightly over 25 cm on the short side, but their 38.2 cm long side exceeds the 34 cm within-limits maximum, so even one sheet makes them oversize. With B4 copy paper in a Kaku 0, up to 4 sheets (about 46 g) cost ¥260 and 5 to 13 sheets ¥290. If the same documents fit in a Kaku 2, they cost only ¥140 up to 50 g. Even B4 documents work out ¥120 cheaper if you fold them in half and send them in a Kaku 2.

Measuring the 3 cm thickness correctly

Thickness is the most disputed point in deciding between within limits and oversize. The post office checks whether the item passes through a special gauge with a 3 cm slot. For a bulging envelope, if the thickest part doesn't pass, it's oversize.

1. 1

   Seal it before measuring

   Before sealing, the open flap makes it look thinner. Close it with tape or glue and measure it as it will be sent.

2. 2

   Lay it on a flat desk and stand a ruler up

   Put the envelope on a desk and hold a ruler vertically against the thickest point. Pressing down from above gives a thinner reading than reality, so just rest your hand lightly.

3. 3

   Make a 3 cm gap and try passing it through

   Stand two books 3 cm apart and see whether the envelope slides through the gap. It's a close match for the post office gauge.

4. 4

   If there's only 2–3 mm to spare, go to a counter

   Depending on the item's shape, the reading changes with how you hold the ruler. If it's borderline, having it measured at the counter is the sure way.

Practice: which category is this size and weight?

Let's apply the order above to combinations of size, thickness and weight that often cause confusion. Sizes are long side × short side × thickness.

As in the third row, even a standard-size item becomes teikeigai once it's over 1 cm thick, even at 40 g. That's the within-limits up-to-50 g rate of ¥140, just ¥30 more than the ¥110 teikei rate, but if you only put on a ¥110 stamp, it's underpaid. The sixth row shows a mere 5 mm of thickness costing ¥150 more. When sending items, simply packing with the 3 cm limit in mind changes the postage.

Items that tend to become oversize, and how to avoid it

• Thick books and magazines: hardcovers and thick magazines easily exceed 3 cm. Send them as two packages, or if each is 3 cm or less, they stay within limits
• Small boxes (accessories, cosmetics, gadgets): if the box is taller than 3 cm, it's oversize. Taking it out of the box and wrapping it in padding can bring it within limits
• Documents and posters B4 or larger: the long side exceeds 34 cm. Fold B4 in half and put it in a Kaku 2 to stay within limits
• Clothing: folding makes it thick. Get it under 3 cm with a compression bag and it's within limits
• Documents packed tightly into a gusseted envelope: even if light, the thickness makes it oversize

The basics for avoiding oversize are fold it, split it and drop the box. But there's no point forcing things in and damaging the contents or having the envelope burst open. For items you want tracked or insured, or anything fragile, consider a different way of sending in the first place rather than teikeigai mail.

Once it's oversize, compare other ways of sending

Oversize rates are higher, so there are times when a flat-rate envelope service is cheaper. These are the prices and size limits of the special envelopes you can buy at the post office.

For example, a 400 g box slightly thicker than 3 cm costs ¥660 as oversize, but if it fits within 34 × 24.8 cm, Letter Pack Plus at ¥600 is cheaper and comes with tracking. On the other hand, if a 100 g item has merely become oversize, it's ¥290, cheaper than a Letter Pack. For small items around A5, you could also keep them within 2 cm and use Smart Letter (¥210). For a detailed comparison, see Tokutei Kiroku, Kan'i Kakitome or Letter Pack: which is cheapest?.

Related reading

• How many sheets fit in teikei mail: How many A4 sheets fit in standard-size mail?
• Postage for a Kaku 2 envelope: How much postage for a Kaku 2 envelope?
• Using up old-rate stamps: How much to add to an ¥84 stamp?

FAQ

What's the difference between teikeigai within limits and oversize?

Within 34 cm on the long side, 25 cm on the short side, 3 cm thick and 1 kg is within limits. Beyond that, up to 60 cm on the long side, 90 cm for the three sides combined and 4 kg is oversize. Up to 50 g, within limits costs ¥140 and oversize ¥260.

How much does oversize mail cost?

At the October 2024 rates: ¥260 up to 50 g, ¥290 up to 100 g, ¥390 up to 150 g, ¥450 up to 250 g, ¥660 up to 500 g, ¥920 up to 1 kg, ¥1,350 up to 2 kg and ¥1,750 up to 4 kg.

Is a Kaku 0 envelope oversize?

Yes. A Kaku 0 is 287 × 382 mm, and its long side exceeds the 34 cm within-limits maximum, so even with one sheet it takes the oversize rate of ¥260 (up to 50 g). Kaku 1 (270 × 382 mm) is the same.

How should I measure the 3 cm thickness?

Seal it, lay it on a flat desk and hold a ruler vertically against the thickest part. The post office checks whether it passes through a special gauge with a 3 cm slot, so standing books 3 cm apart and sliding it through the gap gives a close result.

What if something is within-limits size but over 1 kg?

Within limits only goes up to 1 kg, so over 1 kg it takes the oversize up-to-2 kg rate (¥1,350). Over 4 kg, it can't be sent as teikeigai mail.