How to Measure Without a Ruler
You do not need a ruler to get a good measurement. Many everyday things have exact, known sizes.
1. Use your screen
Open the online ruler on your phone or laptop, calibrate it once with a card and measure objects up to the length of your screen.
2. Objects with standard sizes
| Object | Size |
|---|---|
| Bank or credit card | 85.60 x 53.98 mm (3.37 x 2.125 in) |
| A4 paper | 210 x 297 mm |
| US Letter paper | 8.5 x 11 in (215.9 x 279.4 mm) |
| US dollar bill | 156 x 66.3 mm (6.14 x 2.61 in) |
| US quarter | 24.26 mm across |
| 1 euro coin | 23.25 mm across |
| AA battery | 50.5 mm long |
| Standard sticky note | 76 x 76 mm (3 x 3 in) |
Lay the object along what you measure and count how many fit. Five card widths in a row are 42.8 cm.
3. Your own body
Measure these once with a real ruler and remember them:
- Thumb width at the knuckle, often about 2 to 2.5 cm (close to 1 inch).
- Hand span from thumb tip to little finger tip, often 18 to 23 cm.
- Your normal step, often 70 to 80 cm.
4. Paper folding
Fold an A4 sheet in half along the long side to get 148.5 mm, again for 105 mm. Folding Letter paper gives 5.5 and 4.25 inches.
5. Your phone itself
Look up your phone’s height and width in the spec sheet. An iPhone 16 is 147.6 x 71.6 mm. Use it as a ruler for longer items.
Long objects
For anything longer than your screen, mark where the ruler ends, slide the object and measure the rest. Add the parts. For rooms and furniture, a tape measure is still the best tool.
Want to check what your screen can measure? The screen size calculator shows its width and height in cm and inches.