Japanese sizes are written in metric units because a statute requires it. The Measurement Act bans any unit outside the statutory set from being used in a transaction or a certification, and a breach carries a fine of up to 500,000 yen. What that produces is visible in the documents that put numbers on size: a defence procurement specification for men’s shoes whose type column is a foot length running from 23 to 30 centimetres, an airline page that caps a cabin bag at 55 by 40 by 25 centimetres, and a courier page on which the word size means the sum of three dimensions.
The Measurement Act bans non-statutory units in any transaction
The Measurement Act dates from 1992. Article 2 paragraph 1 sets out the quantities it governs in two items. Item 1 is a single list that starts with length, mass and time and runs through seventy-two entries, counted here, to dose equivalent rate. Item 2 adds fineness, specific gravity and anything else named by cabinet order, so the list does not close with the seventy-two. Article 3 says the units for the quantities in Appended Table 1 are the ones in that table, and that their definitions follow the resolutions of the General Conference on Weights and Measures and other international decisions and practice, as set out by cabinet order.
Article 8 paragraph 1 is the operative rule. Units other than those set by Articles 3 to 5, which the Act calls non-statutory units, may not be used in a transaction or a certification for any of the quantities in Article 2 paragraph 1 item 1. Article 9 paragraph 1 goes further and forbids selling, or displaying for sale, a measuring instrument used to measure one of those quantities that carries a scale or marking in a non-statutory unit. Article 173 sets the penalty for breaching either of those at a fine of up to 500,000 yen; Article 172 sets up to six months of confinement or the same fine, or both, for a separate list of breaches.
The exceptions are at the border. Article 8 paragraph 3 lifts the ban in three cases, which are transactions and certifications concerning goods to be exported, those concerning the import of goods, and those named by cabinet order either between people who have no domicile or residence in Japan and other people named by cabinet order, or between such people and anyone else. Article 9 paragraph 2 lifts the instrument ban for measuring instruments to be exported and others named by cabinet order. The inch on an imported box comes through a different door. Article 5 of the Act’s own supplementary provisions leaves the yard and pound units and their definitions to cabinet order, and then deems them statutory units, for the time being, in two cases: transactions and certifications about the operation of aircraft and other aviation matters named by cabinet order, and transactions and certifications concerning imported goods whose quantity is already marked in those units and which are named by cabinet order. Article 6 of the same supplementary provisions does the same, for the time being, for metric horsepower in transactions about internal combustion engines and others named by cabinet order.
A defence specification shows what a shoe size is made of
Japanese Industrial Standard S 5037 is titled Shoe sizes, and it is the document the size letters come from. The standard itself is sold by the standards body and was not read here, but a government procurement specification that cites it was, and it shows how the system is used.
Defence Specification DSP S 5001D covers men’s shoes for male Self-Defence Force personnel and male students of the National Defense Academy and the National Defense Medical College. It was established on 28 November 1974 and last revised on 30 August 2023. Its type column is headed foot length in centimetres, and it runs from 23 to 30 plus one entry marked SS for a special size, with a stock number against each: 8430-299-0085-5 for the 23 and 8430-299-0086-5 for the SS.
The foot girth is not given as a number in that specification. Clause 2.3.2 states that the girth, for every type except SS, is the EEE of JIS S 5037, so the standard supplies the letter and the specification simply points at it. For the SS entry the foot length, girth and width are measured according to the attached figure 1 of JIS S 5037 and then written into the procurement order.
Fifteen lasts, and each step is five millimetres
The specification’s last table has fifteen rows between 23 and 30 centimetres of foot length, and each row differs from the one before it by five millimetres of overall last length, which is the half-centimetre step in the size name. The eight whole-centimetre rows are below; the seven rows left out are the half sizes that sit between them, and they carry the intermediate figures.
| Foot length (cm) | Overall last length (mm) | Last bottom length (mm) | Toe spring (mm) | Toe width (mm) | Ball girth (mm) |
|---|---|---|---|---|---|
| 23 | 252 | 249 | 20.0 | 67.8 | 227 |
| 24 | 262 | 259 | 21.0 | 69.4 | 235 |
| 25 | 272 | 269 | 22.0 | 71.0 | 243 |
| 26 | 282 | 279 | 23.0 | 72.6 | 251 |
| 27 | 292 | 289 | 24.0 | 74.2 | 259 |
| 28 | 302 | 299 | 25.0 | 75.8 | 267 |
| 29 | 312 | 309 | 26.0 | 77.4 | 275 |
| 30 | 322 | 319 | 27.0 | 79.0 | 283 |
Across the whole table the overall last length rises from 252 to 322 millimetres, a span of 70 millimetres over fourteen steps, which is the five millimetres a step quoted above; that division is arithmetic done here. Ball girth rises four millimetres a step, from 227 to 283. A width column, which is not among the columns set out here, rises one millimetre a step from 84 to 98. The table ends with a tolerance row carrying four figures, plus or minus 1.5, 1.0, 2.0 and 3.0 millimetres.
The same specification fixes other dimensions in the same units. The upper leather must be at least 1.7 millimetres thick. The grooves in the outsole and heel must be no deeper than 3 millimetres, and the sole has to be built so that it does not slip on snow-covered roads or on ship decks. Shoes are made by the cement process of JIS S 5050. The shipping carton is standardised at 770 by 340 by 615 millimetres. The shank has to sit at least 25 millimetres into the heel area from the heel breast, and it must not reach into the lasting allowance.
ANA’s cabin limits are two boxes and one shared weight
Airlines publish their limits in the same units, and they publish them as boxes rather than as a single number. The international baggage page of ANA, read on 9 October 2026, allows two items into the cabin on flights operated by the ANA Group: one piece of carry-on baggage and one personal item.
For the carry-on piece the limit depends on the aircraft. On an aircraft with 100 seats or more the three sides must total within 115 centimetres and fit within 55 by 40 by 25 centimetres. On an aircraft with fewer than 100 seats the total is within 100 centimetres and the box is 45 by 35 by 20 centimetres. The personal item has its own figure, within 40 by 30 by 20 centimetres, and the page states that this was updated for flights boarding on or after 1 July 2026, with the carry-on piece unchanged. The weight limit covers both items together: up to 10 kilograms in total.
A parcel size in Japan is a sum, not a box
The word size appears again on parcels, and it means something else. Yamato Transport’s own page for its Takkyubin service defines the range it accepts as size 60 through size 200, where the qualifying figures are a total of length, width and height within 200 centimetres and a weight up to 30 kilograms. The same page adds that no single side may run beyond 170 centimetres, and that the figure drops to 100 centimetres for a parcel that cannot be turned upside down or that otherwise has conditions set on how it travels. The compensation limit is stated as up to 300,000 yen including tax for each parcel, and the page records that the notified fares and charges were revised on 1 October 2025.
The airport version of the same service adds its own numbers. Parcels over 30 kilograms are not handled. Sending a parcel to an airport attracts an airport handling charge of 660 yen including tax, on top of the fare. Time-slot delivery is offered only on the return leg, and so is cash on delivery. Three entries in the discount list are marked unavailable on this service and are not marked that way on the ordinary Takkyubin page: the multiple-parcel reduction, the service that lets a parcel be picked up at a branch office, and the same-prefecture fare. What is left is 100 yen off a parcel for handing it in over a counter, or 150 yen for a Kuroneko Members hand-in, 60 yen off for each of four digital waybill routes, 200 yen off a round-trip parcel, and percentage cuts of up to 15 per cent on the members card and 12 per cent through the Nyan Pay wallet.
What these documents do not convert
None of the documents read here prints a conversion table between Japanese and foreign sizes. The defence specification gives foot length and girth and cites the standard for the letter; it does not mention European or American size numbers at all. The airline page gives centimetres and kilograms and no inches or pounds. The Measurement Act governs units rather than labels, and the articles read here say nothing about how a garment or a shoe should be marked.
Two other things are absent. The text of JIS S 5037, which holds the girth and width tables behind the letter EEE, was not read here, so nothing on this subject goes beyond the two clauses the specification quotes. And neither the Act nor the specification sets a size for clothing, a ring or a bed; the Act’s own list of quantities is about length and mass, not about garment labelling.
The figures with the shortest life are the airline ones, because the page itself carries a change dated 1 July 2026 and the carrier can revise either box at any time, and the Yamato charges, which moved on 1 October 2025 and are notified fares. The defence specification has stood since 1974 with its last revision in 2023, and the Measurement Act text read here is the version standing on the government database in October 2026.
Sources Checked
e-Gov law search, the government database of current Japanese law — Measurement Act, Act No. 51 of 1992
Confirmed the list of governed quantities in Article 2 paragraph 1 item 1, which begins with length, mass and time and which was counted here at seventy-two entries ending with dose equivalent rate, the second item of the same paragraph naming fineness, specific gravity and anything else set by cabinet order, the rule in Article 3 that units follow Appended Table 1 and are defined in line with the General Conference on Weights and Measures by cabinet order, the ban in Article 8 paragraph 1 on using non-statutory units in a transaction or certification for those quantities, the three exceptions in Article 8 paragraph 3 covering goods to be exported, the import of goods and transactions named by cabinet order involving people with no domicile or residence in Japan, the ban in Article 9 paragraph 1 on selling measuring instruments used for those quantities and scaled in non-statutory units with the export exception in paragraph 2, Article 5 of the supplementary provisions deeming yard and pound units statutory for the time being in aviation transactions and in transactions over imported goods already marked in them, Article 6 of the supplementary provisions doing the same for metric horsepower in transactions about internal combustion engines, the fine of up to 500,000 yen in Article 173 for breaches of Articles 8 and 9, and the six months of confinement or 500,000 yen in Article 172 for the separate list.
https://laws.e-gov.go.jp/law/404AC0000000051
Ministry of Defense, Acquisition, Technology and Logistics Agency — Defence Specification DSP S 5001D, Shoes, Men’s, established 28 November 1974 and revised 30 August 2023
Confirmed the scope covering male Self-Defence Force personnel and male students of the National Defense Academy and the National Defense Medical College, the type column headed foot length in centimetres running from 23 to 30 with an SS entry for a special size, the stock numbers 8430-299-0085-5 and 8430-299-0086-5, the citation of JIS S 5037 under the title Shoe sizes and of JIS S 5050 for leather shoes and the cement process, the rule in clause 2.3.2 that girth is the EEE of JIS S 5037 for all types except SS and that SS dimensions are measured under attached figure 1 of that standard, the fifteen-row last table with overall last length from 252 to 322 millimetres, ball girth from 227 to 283 millimetres and width from 84 to 98 millimetres, together with last bottom length, toe spring and toe width, the tolerance row of plus or minus 1.5, 1.0, 2.0 and 3.0 millimetres, the upper leather thickness of at least 1.7 millimetres, the outsole groove depth of no more than 3 millimetres with the requirement that soles not slip on snow or on ship decks, the shank inserted at least 25 millimetres into the heel area without reaching the lasting allowance, and the standard carton of 770 by 340 by 615 millimetres.
https://www.mod.go.jp/atla/dsp/S/s5001.pdf
ANA — international flights baggage page, read on 9 October 2026
Confirmed that two items may be taken into the cabin, one piece of carry-on baggage and one personal item, that the carry-on piece must total within 115 centimetres and fit within 55 by 40 by 25 centimetres on aircraft with 100 seats or more and within 100 centimetres and 45 by 35 by 20 centimetres on aircraft with fewer than 100 seats, that the personal item limit is within 40 by 30 by 20 centimetres for flights boarding on or after 1 July 2026 with the carry-on size unchanged, and that the combined weight limit is 10 kilograms.
https://www.ana.co.jp/en/jp/guide/boarding-procedures/baggage/international/
Yamato Transport — Takkyubin service page, read on 9 October 2026
Confirmed that the service covers size 60 through size 200, defined as a total of length, width and height within 200 centimetres and a weight up to 30 kilograms, that no single side may run beyond 170 centimetres and that the figure drops to 100 centimetres for parcels with conditions set on how they travel, that the compensation limit is up to 300,000 yen including tax per parcel, that the notified fares and charges were revised on 1 October 2025, and that the multiple-parcel reduction, the branch-office pickup discount and the same-prefecture fare are all listed without a mark of unavailability.
https://www.kuronekoyamato.co.jp/ytc/customer/send/services/takkyubin/
Yamato Transport — Airport Takkyubin service page, read on 9 October 2026
Confirmed that parcels over 30 kilograms are not handled, that sending to an airport carries an airport handling charge of 660 yen including tax, that time-slot delivery and cash on delivery are offered on the return leg only, that the multiple-parcel reduction, the branch-office pickup service and the same-prefecture fare are each marked unavailable on this page, and that the discounts carried without that mark are 100 yen a parcel for handing it in, 150 yen for a Kuroneko Members hand-in, 60 yen for each of four digital waybill routes, 200 yen for a round-trip parcel, up to 15 per cent on the members card and 12 per cent through Nyan Pay.
https://www.kuronekoyamato.co.jp/ytc/customer/send/services/airport/
Last updated: October 2026
