For domestic Yu-Pack, add the parcel’s length, width and height in centimetres, then choose the smallest size band that contains that total. Check weight separately: ordinary Yu-Pack accepts up to 25 kg, with a maximum three-side total of 170 cm. A parcel can pass one test and fail the other. This guide is based on Japan Post’s published rules, not a test shipment. Japan Post: Yu-Pack size and weight
“Size 80” means a three-side total, not an 80 cm box
The number is the upper limit of the combined dimensions. It is not the maximum permitted length of every side, and it is not the volume in litres.
| Size band | Maximum length + width + height |
|---|---|
| 60 | 60 cm |
| 80 | 80 cm |
| 100 | 100 cm |
| 120 | 120 cm |
| 140 | 140 cm |
| 160 | 160 cm |
| 170 | 170 cm |
These are Japan Post’s published domestic Yu-Pack bands. A total exactly at a boundary fits that band; a total above it requires the next one. Japan Post: parcel rate categories
For example, a hypothetical packed box measuring 30 × 20 × 10 cm totals 60 cm. If packing makes its height 11 cm instead, the total becomes 61 cm and the dimensions fall in size 80. The 1 cm change does not create a size-61 price.
Measure the outside after adding protection
Prepare the contents and cushioning before taking the measurements you will use for a rate estimate. A shop’s box description is useful for choosing packaging, but check whether its dimensions describe the inside or outside. Measure the finished parcel yourself, including any bulge, rather than pricing the empty box.
For an irregular item, Japan Post says to measure the longest extent in each of the three dimensions and add them. For a sphere, its example is the diameter multiplied by three. This is not a measurement around the item’s curved surface. Japan Post: measuring spherical and irregular parcels
Suppose a safely packaged irregular object has maximum outside dimensions of 45 × 20 × 15 cm. Its hypothetical total is 80 cm. If a protruding part makes the width 23 cm, the total is 83 cm and the size band changes to 100. Do not remove necessary protection just to preserve the earlier estimate.
A small parcel can still need the heavier service
Ordinary Yu-Pack’s weight limit does not rise with each size band. A size-60 parcel and a size-160 parcel are both subject to the ordinary 25 kg ceiling. For weights over 25 kg and up to 30 kg, Japan Post provides Weighted Yu-Pack, with its own handling conditions. Japan Post: ordinary limits, Weighted Yu-Pack
These examples are hypothetical and assume the contents are otherwise eligible:
| Packed dimensions and weight | Dimension result | Weight result |
|---|---|---|
| 30 × 20 × 10 cm; 2 kg | Size 60 | Within ordinary limit |
| 30 × 20 × 10 cm; 26 kg | Size 60 | Check Weighted Yu-Pack |
| 70 × 60 × 41 cm; 5 kg | 171 cm: above the ordinary maximum | Low weight does not fix the size failure |
Do not assume that a heavier parcel can use every ordinary Yu-Pack drop-off option. The heavier service’s page sets its own conditions. It also describes a narrow allowance involving light outer packaging around contents clearly marked as weighing no more than 30 kg; ask Japan Post about that case rather than treating it as a general higher limit. Japan Post: Weighted Yu-Pack conditions
Look up the price only after the category is settled
Once you know the size and weight category, use the official rate table for the sending prefecture and destination, or the calculator linked from Japan Post’s Yu-Pack page. “Size 80” alone is not a nationwide fixed price. Check any applicable service or discount conditions separately. Japan Post: fees and rate lookup
Before looking up a rate, write down four things: the three measured outside dimensions, their sum, the packed weight, and the sending and destination prefectures. If the parcel is close to a boundary, take the packed item to the postal counter for measurement before relying on a home estimate.
This procedure settles a domestic parcel’s measurement category. It does not establish whether the contents are acceptable, promise a delivery day, or set the limits for EMS or other international services. Those require the rules for the actual service you will use.