Shipping box sizes and what they bill at
Common shipping box sizes, what fits in each, how to measure a box, and what each size bills at with Canada Post, Purolator, UPS and FedEx.
Updated
Short answer. Carriers bill a box at its actual weight or its size, whichever is higher. A 12 × 12 × 12 in box holding 5 lb bills at about 10 to 15 lb, depending on the carrier and service. Pick the smallest box that leaves room for padding, and measure it closed, on the outside.
Common box sizes and what fits
| Box | Size | Good for |
|---|---|---|
| Padded mailer | 13 × 10 × 1 | Clothing, a book, other flat or soft goods |
| Small box | 12 × 9 × 4 | Accessories, cosmetics, small electronics |
| Cube | 12 × 12 × 12 | Bottles, small appliances, gift sets |
| Medium box | 16 × 12 × 8 | Shoes, kitchenware, several smaller items |
| Small moving box | 16⅜ × 12⅝ × 12⅝ | Books and other dense goods |
| Large cube | 18 × 18 × 18 | Bedding, pillows, light bulky goods |
| Extra-large box | 24 × 18 × 24 | Duvets, lampshades, the lightest bulky goods |
What each size bills at
The table shows each box at a typical packed weight, billed at each divisor in use. A padded mailer and a medium box bill close to their weight. A 12 in cube at 5 lb already bills at two to three times its weight, and an 18 in cube at 15 lb bills at about 35 to 51 lb.
| Box | ÷ 166Canada Post Regular Parcel | ÷ 139Canada Post Expedited Parcel, Xpresspost and Priority · Purolator Ground · UPS Standard · FedEx | ÷ 115Purolator Express, Express 10:30 AM and Express 9 AM · UPS Expedited, Express Saver and Express |
|---|---|---|---|
| Padded mailer, 13 × 10 × 1 in, 1 lb | 1 lb | 1 lb | 1.1 lb |
| Small box, 12 × 9 × 4 in, 2 lb | 2.6 lb | 3.1 lb | 3.8 lb |
| Cube, 12 × 12 × 12 in, 5 lb | 10.4 lb | 12.4 lb | 15 lb |
| Medium box, 16 × 12 × 8 in, 10 lb | 10 lb | 11.1 lb | 13.4 lb |
| Small moving box, measured 17 × 13 × 13 in, 15 lb | 17.3 lb | 20.7 lb | 25 lb |
| Large cube, 18 × 18 × 18 in, 15 lb | 35.1 lb | 42 lb | 50.7 lb |
| Extra-large box, 24 × 18 × 24 in, 25 lb | 62.5 lb | 74.6 lb | 90.2 lb |
UniUni bills dimensional weight too, but doesn’t publish its divisor, so it isn’t in the table. Try your own box in the calculator
How to measure a box
- Pack and seal the box as it will ship.
- Measure the outside. The longest side is the length; the other two are the width and height.
- Round each side up to the next whole inch, as UPS, FedEx and Purolator do.
- Weigh it and round up to the next pound.
- Multiply the three sides and divide by the carrier’s divisor to get the dimensional weight. The carrier bills whichever weight is higher.
Measure the packed box rather than trusting the size it was sold as. A box stuffed until it bulges measures bigger, and the carrier bills what it measures. Our guide to how to measure a package also covers irregular items.
Size lines that change the price
- Over 48 in on the longest side, 30 in on the second-longest, or 105 in length plus girth: extra handling at UPS and FedEx. Purolator’s line is 48 in.
- Over 1 m (39.4 in) on any side, or 76 cm (30 in) on the second-longest: extra handling at Canada Post.
- Over 118 in length plus girth or 78 in on any side: too big for Canada Post.
- Over 130 in length plus girth: UPS, FedEx and Purolator bill at least 90 lb, and FedEx 2Day and Standard Overnight stop there.
- Over 165 in length plus girth or 108 in long: it has to go as freight.
Choosing the right size
- Pick the smallest box that fits the item with at least 5 cm (2 in) of cushioning around it, as UPS recommends.
- Use a rigid box with its flaps attached, and stay under the weight limit printed on the bottom flap.
- Soft goods go well in a mailer, up to a point: Purolator charges extra for soft packs over 18 in long, and UPS for soft packs bigger than 18 × 14 × 6 in.
- A used box is fine if it’s still rigid. Remove or cover every old label and barcode.
- Keep a few sizes on hand. A mailer, a small box and a medium box cover most small orders, and the bigger sizes cost more to ship than they look.
Price your box at every carrier
Enter its size and weight once and compare each carrier and speed that fits it.
Sources, checked October 11, 2026
Related reading
Price your box at every carrier
Enter its size and weight once and compare each carrier and speed that fits.