There are three practical ways to mail A4 documents within Japan:

  1. Fold the pages into a Nagagata 3 envelope for the lowest ordinary-letter price.
  2. Keep them flat in a Kakugata 2 or 20 envelope and pay the non-standard rate by weight.
  3. Use Letter Pack Light or Plus when tracking or a predictable flat price matters.

The best choice depends on whether the pages can be folded, the sealed weight and thickness, and how the recipient should receive them.

Quick comparison

Option Current price Limits that matter Tracking Delivery
Folded standard letter ¥110 Standard dimensions, ≤10 mm, ≤50 g No Mailbox
Flat non-standard letter From ¥140 Rate by weight; specified size ≤340 × 250 × 30 mm and ≤1 kg No by default Mailbox when deliverable
Letter Pack Light ¥430 Japan Post envelope, ≤30 mm, ≤4 kg Yes Mailbox
Letter Pack Plus ¥600 Japan Post envelope, ≤4 kg; seal must close Yes Face-to-face, signature or seal

Prices checked September 12, 2026. Letter Pack is domestic-only and uses its own prepaid envelope.

Option 1: fold A4 into a standard-size letter

A4 paper folded in thirds fits a Nagagata 3 (長形3号) envelope measuring 120 × 235 mm. That envelope matches the maximum length and width for Japan Post standard-size mail.

The complete item must still be no more than 10 mm thick and 50 g. If it meets every condition, the current ordinary postage is ¥110.

This is usually best for routine notices, forms, copies, and correspondence that can be creased. It is not appropriate when the recipient needs a flat original, a certificate must not be folded, or a stiff folder pushes the thickness over the limit.

Option 2: keep A4 flat in a non-standard envelope

Use Kakugata 2 (角形2号, 240 × 332 mm) or Kakugata 20 (角形20号, 229 × 324 mm) to hold A4 paper flat. Both are larger than the standard-letter limit, so ordinary postage follows the non-standard table.

For an item within 340 × 250 × 30 mm and no more than 1 kg, current rates are:

Sealed weight Ordinary non-standard postage
Up to 50 g ¥140
Up to 100 g ¥180
Up to 150 g ¥270
Up to 250 g ¥320
Up to 500 g ¥510
Up to 1 kg ¥750

The envelope, documents, plastic folder, clips, labels, and tape all count. A typical clear folder also adds thickness and weight, so never price the paper alone.

If you are buying envelopes now, compare the exact sizes in Japanese Envelope Sizes.

Option 3: use Letter Pack Light for tracking

Letter Pack Light costs ¥430 anywhere in Japan. It uses a designated 340 × 248 mm prepaid envelope, accepts correspondence, includes tracking, and has limits of 30 mm thickness and 4 kg. Delivery is to the recipient’s mailbox.

No stamp is needed on a current ¥430 Letter Pack envelope. Before mailing, remove and keep the tracking-number sticker. Japan Post accepts Letter Pack Light at postal counters and in post boxes that can physically accept it.

It becomes a particularly useful comparison when flat ordinary mail is over 250 g: the ordinary rate rises to ¥510 at the next band, while Letter Pack Light remains ¥430 if its own limits and content rules are satisfied. Price is not the only difference—Letter Pack adds tracking, but Japan Post states that it is not covered by compensation for damage or loss.

Option 4: use Letter Pack Plus for hand delivery

Letter Pack Plus costs ¥600 anywhere in Japan, includes tracking, and is delivered face-to-face with a signature or receipt seal. It accepts up to 4 kg in its designated A4-size envelope.

Unlike Light, Plus can exceed 30 mm in thickness as long as the contents fit and the designated envelope can be properly closed. It is useful when mailbox delivery is not suitable, but it still has no compensation. Do not treat tracking as insurance.

Letter Pack Plus can be handed over at a postal counter, placed in a compatible post box, or collected by Japan Post. A counter is the simplest choice for a bulky envelope.

Which option should you choose?

Use this decision order:

  1. Must the document stay flat? If no, test a folded Nagagata 3 letter. If yes, continue.
  2. Do you need tracking? If no, compare the sealed weight with the ordinary non-standard table. If yes, continue.
  3. Is the sealed item 30 mm or thinner? If yes, Letter Pack Light may work. If no, consider Letter Pack Plus.
  4. Is the content valuable or irreplaceable? If yes, neither Letter Pack’s tracking nor ordinary mail provides compensation. Ask Japan Post which registered or insured service is appropriate.

For exact ordinary postage, enter the sealed measurements in the Japan Postage Calculator. Its result also compares Letter Pack Light when that option fits.

Prepare the document correctly

  • Put the destination and return address on before the envelope becomes bulky.
  • Use a protective folder only when its extra weight and thickness are justified.
  • Remove unnecessary metal clips that can catch or create a pressure point.
  • Seal every flap; do not rely on a string or loose tuck closure.
  • Keep a separate scan of important documents.
  • For Letter Pack, write a useful content description and keep the tracking sticker.

Cash, precious metals, hazardous materials, fragile objects, perishables, and difficult-to-replace items are not suitable for Letter Pack. Cash must not be put in an ordinary document envelope either; ask for Japan Post’s registered-cash procedure.

When to use the counter

Take the item to a post-office counter when it sits close to a size or weight boundary, contains an original that cannot easily be replaced, needs proof beyond basic tracking, or must arrive by a particular deadline. A calculator can identify a category, but it cannot inspect the contents or promise a delivery date.

Sources checked

Sources reviewed September 12, 2026. Rates and conditions can change; confirm current Japan Post information before mailing.