OneTaskBy Tim King · Updated
Package Size Calculator
Box Size, Girth and Dimensional Weight for an Item
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How the Package Size Calculator works
This package size calculator works out the shipping box an item needs once padding goes round every side, giving the inside and outside box size, length plus girth, void fill and the dimensional weight a carrier will charge for.
How the package size calculator works
Each inside dimension is the item dimension plus padding on both sides, and each outside dimension adds the wall thickness twice. The formula for length plus girth is longest side + 2 × (the other two sides), the measure carriers use for size limits. Dimensional weight is the outside volume in cm³ ÷ 5,000 for kg, or in in³ ÷ 139 for lb. Void fill is the inside volume minus the item's volume.
First example. An item of 30 × 20 × 10 cm with 5 cm of padding needs a 40 × 30 × 20 cm inside box. With 4 mm walls the outside is 40.8 × 30.8 × 20.8 cm, length plus girth is 144 cm, void fill is 18 litres and the dimensional weight is 5.23 kg.
Second example. A 12 × 9 × 4 in item with 2 in of padding needs a 16 × 13 × 8 in inside box. With ¼ in walls the outside is 16.5 × 13.5 × 8.5 in, length plus girth is 60.5 in and the dimensional weight at ÷139 is 13.62 lb.
How many cm of padding does an item need? About 5 cm (2 in) on every side suits most fragile items in a single box. Heavy or very fragile items are safer double boxed, with 5 cm of padding in each box.
Carriers set their own divisors: 5,000 is common for courier services and 6,000 for many postal and economy services. Check your carrier's figure before you rely on the dimensional weight.
Common shipping box sizes in cm with volume, length plus girth and dimensional weight
| Box (cm) | Volume | Length + girth | Dim weight ÷5000 | Dim weight ÷6000 |
|---|---|---|---|---|
| 15 × 15 × 15 | 3.4 L | 75 cm | 0.68 kg | 0.56 kg |
| 20 × 15 × 10 | 3 L | 70 cm | 0.6 kg | 0.5 kg |
| 20 × 20 × 20 | 8 L | 100 cm | 1.6 kg | 1.33 kg |
| 25 × 20 × 10 | 5 L | 85 cm | 1 kg | 0.83 kg |
| 25 × 20 × 15 | 7.5 L | 95 cm | 1.5 kg | 1.25 kg |
| 30 × 20 × 15 | 9 L | 100 cm | 1.8 kg | 1.5 kg |
| 30 × 20 × 20 | 12 L | 110 cm | 2.4 kg | 2 kg |
| 30 × 25 × 20 | 15 L | 120 cm | 3 kg | 2.5 kg |
| 30 × 30 × 30 | 27 L | 150 cm | 5.4 kg | 4.5 kg |
| 35 × 25 × 15 | 13.1 L | 115 cm | 2.63 kg | 2.19 kg |
| 35 × 25 × 25 | 21.9 L | 135 cm | 4.38 kg | 3.65 kg |
| 40 × 30 × 20 | 24 L | 140 cm | 4.8 kg | 4 kg |
| 40 × 30 × 30 | 36 L | 160 cm | 7.2 kg | 6 kg |
| 40 × 40 × 40 | 64 L | 200 cm | 12.8 kg | 10.67 kg |
| 45 × 35 × 25 | 39.4 L | 165 cm | 7.88 kg | 6.56 kg |
| 45 × 35 × 35 | 55.1 L | 185 cm | 11.03 kg | 9.19 kg |
| 50 × 40 × 30 | 60 L | 190 cm | 12 kg | 10 kg |
| 50 × 40 × 40 | 80 L | 210 cm | 16 kg | 13.33 kg |
| 50 × 50 × 50 | 125 L | 250 cm | 25 kg | 20.83 kg |
| 60 × 40 × 30 | 72 L | 200 cm | 14.4 kg | 12 kg |
| 60 × 40 × 40 | 96 L | 220 cm | 19.2 kg | 16 kg |
| 60 × 50 × 40 | 120 L | 240 cm | 24 kg | 20 kg |
| 60 × 60 × 60 | 216 L | 300 cm | 43.2 kg | 36 kg |
FAQ
What is length plus girth?
Girth is the distance round the parcel at its thickest point, twice the width plus twice the height. Add the length, the longest side, to get length plus girth. Carriers use it to set maximum sizes and oversize fees.
How much padding should a package have?
Allow around 5 cm (2 in) of cushioning on every side for fragile goods, and less for sturdy items such as clothing or books. The padding must stop the item touching any wall when the box is shaken.
Why is the outside box size bigger than the inside?
Box sizes are often listed as inside dimensions, but carriers measure the outside. Each wall adds its thickness on both sides, about 4 mm for single wall board and 7 mm for double wall board.
What is void fill?
Void fill is the packing material, such as paper, air pillows or foam, that fills the space between the item and the box. The calculator gives its volume so you can estimate how much material to buy.
How do I reduce dimensional weight?
Use the smallest box that keeps the padding you need, and cut down tall boxes to fit. Removing just 2 cm from each side of a 40 × 30 × 20 cm box cuts the dimensional weight by a fifth.
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