Core length conversion factors
| From | To | Operation |
|---|---|---|
| cm | mm | × 10 |
| mm | cm | ÷ 10 |
| cm | inches | ÷ 2.54 |
| inches | cm | × 2.54 |
| cm | feet | ÷ 30.48 |
| feet | cm | × 30.48 |
| inches | feet | ÷ 12 |
| feet | inches | × 12 |
These factors apply to each one-dimensional measurement: length, width, height, depth or thickness.
Example: 78 × 48 × 33 cm to inches
Divide each value by 2.54: 78 cm ≈ 30.71 in, 48 cm ≈ 18.90 in, and 33 cm ≈ 12.99 in. The converted dimensions are approximately 30.71 × 18.90 × 12.99 inches.
Example: 6000 × 100 × 50 mm to metres and centimetres
Divide millimetres by 1,000 for metres: 6 × 0.1 × 0.05 m. Divide by 10 for centimetres: 600 × 10 × 5 cm. Keep the same order and labels while converting so length does not get confused with width or thickness.
Converting a dimension is not the same as converting area
If a rectangle is 100 cm × 50 cm, converting each side gives about 39.37 in × 19.69 in. Area conversion is different because the factor is squared. 1 m² equals about 10.7639 ft², not 3.28084 ft².
Volume conversion needs cubic factors
For a box, convert all three dimensions first or calculate volume in one cubic unit and then convert the cubic result. 1 litre equals 1,000 cm³. 1 cubic foot equals about 28.3168 litres. Using a linear conversion factor on a volume value is a common mistake.
Feet and inches together
A dimension like 5 ft 8 in can be converted to total inches: 5 × 12 + 8 = 68 in. In centimetres, 68 × 2.54 = 172.72 cm. This is useful when comparing product dimensions listed in different formats.
Rounding for fit and manufacturing
For general shopping, two decimal places are usually enough. For machining, fabrication or tight clearances, use the precision required by the drawing and account for tolerances. Do not round dimensions early when several conversions or multiplications follow.
Keep labels attached to numbers
When converting a list such as 72 H × 12 W × 18 D inches, preserve H, W and D beside the converted values. The result is approximately 182.88 H × 30.48 W × 45.72 D cm. This prevents orientation mistakes.
Frequently asked questions
How do I convert cm to inches?
Divide centimetres by 2.54.
How do I convert millimetres to centimetres?
Divide millimetres by 10.
How many centimetres are in one foot?
30.48 cm.
Should I convert length, width and height separately?
Yes. Convert each dimension individually and keep the labels/order consistent.
Enter your own values, keep the assumptions visible and use this guide to understand the formula behind the result.