When selling secondhand items or handmade crafts on flea market apps (Mercari, Yahoo Auctions, Rakuma), one of the most frustrating experiences is having a parcel returned or incurring unexpected shipping surcharges due to exceeding package thickness limits.
Sellers often wonder: "Will this book pass the 3cm thickness threshold?", "How much thickness does bubble wrap add?", or "How can I verify parcel dimensions without purchasing specialized plastic thickness gauge rulers?"
This comprehensive guide details strict shipping thickness limits (1cm, 2cm, and 3cm thresholds), shows how to calculate packaging material inflation, and explains how to use Jougi Online on your smartphone as a digital sizing caliper.
1. Major Discount Shipping Services & The "Thickness Thresholds"
| Service | Approx. Cost | Max Thickness | Max Dimensions | Tracking |
|---|---|---|---|---|
| Standard Letter (Teikei) | ¥84 – ¥94 | 1.0 cm (10 mm) | 23.5 × 12.0 cm (Nagagata-3) | No tracking |
| Smart Letter | ¥180 | 2.0 cm (20 mm) | 25.0 × 17.0 cm (A5 envelope) | No tracking |
| Click Post (Japan Post) | ¥185 | 3.0 cm (30 mm) | 34.0 × 25.0 cm (A4 size) | Tracked |
| Yu-Packet (Mercari) | ¥215 – ¥230 | 3.0 cm (30 mm) | Max length 34cm, sum of 3 sides ≤ 60cm | Tracked & Anonymous |
| Nekopos (Yamato / Mercari) | ¥210 | 3.0 cm (30 mm) | 31.2 × 22.8 cm (A4 size) | Tracked & Anonymous |
2. Packaging Material Thickness Inflation
Never measure just the naked product! Cushioning materials add significant bulk:
- Bubble Wrap (Single Layer): Adds +4.0 mm to +5.0 mm per layer (+8 to 10 mm total when wrapped around).
- Cardboard Sandwich (for Trading Cards / Badges): Adds +3.0 mm to +5.0 mm.
- Envelope Seam Bulge: Adds +1.0 mm to +2.0 mm at the tape closure.
3. Measuring Thickness Without a Physical Sizing Gauge
If you don't own a plastic measuring ruler with slot cutouts, you can measure thickness using two books on a flat desk:
- Place two thick hardcover books on a flat table.
- Sandwich your package gently between the two books.
- Measure the gap between the books using Jougi Online on your smartphone.
You can also use stacked coins as thickness benchmarks: ten 1-Yen coins stack up to exactly 15.0 mm (1.5 cm), and twenty coins equal 30.0 mm (3.0 cm).
4. Checking 1cm, 2cm & 3cm Limits with Jougi Online
Open Jougi Online on your phone, set Pin A to 0.0 mm, and move Pin B to 30.0 mm (or 10.0 / 20.0 mm). Place your parcel edge against the screen bezel to verify whether the package fits within the boundary lines before heading to the post office.