How to measure something without a ruler
You don’t need a ruler to measure something reasonably accurately. Plenty of things in your wallet and desk are made to an exact, standard size. Lay one next to the object, or line several up end to end.
Cards
| Item | Size |
|---|---|
| Bank card, ID card, most membership cards | 85.60 × 53.98 mm (3.37 × 2.13 in) |
Card sizes are set by an international standard (ISO/IEC 7810 ID-1), so almost every card in your wallet is the same. The long side is a handy 8.5 cm, and the short side just under 5.4 cm.
Coins
Coin sizes are set by the mint and are very consistent.
| Coin | Diameter |
|---|---|
| US penny (1¢) | 19.05 mm (0.75 in) |
| US nickel (5¢) | 21.21 mm (0.835 in) |
| US dime (10¢) | 17.91 mm (0.705 in) |
| US quarter (25¢) | 24.26 mm (0.955 in) |
| 1 euro cent | 16.25 mm |
| 10 euro cents | 19.75 mm |
| 1 euro | 23.25 mm |
| 2 euros | 25.75 mm |
| UK 1p | 20.3 mm |
| UK £1 | 23.43 mm |
Three US pennies in a row is almost exactly 57 mm, and four quarters about 97 mm, just short of 10 cm.
Paper
| Item | Size |
|---|---|
| A4 paper | 210 × 297 mm |
| US Letter paper | 8.5 × 11 in (215.9 × 279.4 mm) |
| US dollar bill | 6.14 × 2.61 in (156 × 66.3 mm) |
A sheet of printer paper is a good long reference. Fold it in half across its length, then in half again, and the creases mark quarters of its length. More paper sizes are in the paper size guide.
Your own hand
Body measurements vary from person to person, but once you’ve measured your own they’re always with you. Measure these once with a real ruler and remember them:
- the width of your thumb at the knuckle (often close to 2–2.5 cm, roughly an inch);
- your hand span, from thumb tip to little finger tip, spread wide;
- the length of your stride, for pacing out a room.
Or use your screen
If you have a phone or computer nearby, the online ruler works as a real ruler once it’s calibrated. Calibrating uses a bank card from the list above.