How to Measure Without a Ruler: 10 Everyday Items You Can Use

You need to measure something, but there is no ruler in sight. Good news: several common items have precise, standardized dimensions that make them excellent emergency rulers. Here are 10 items you almost certainly have nearby, with their exact sizes.

1. Credit Card or Debit Card

85.60 by 53.98 mm (3.37 by 2.13 inches). Every bank card worldwide is identical because they all follow ISO/IEC 7810 ID-1. The world most reliable everyday ruler. Use it to calibrate our online ruler for unlimited measurement after.

2. US Dollar Bill

156 by 66.3 mm (6.14 by 2.61 inches). All denominations of US paper currency are the exact same size. A folded dollar equals 78 mm. A quarter-folded dollar equals 39 mm.

3. Euro Banknote (10 Euro)

127 by 67 mm. Each euro denomination is a different size. The 5 euro note is 120 by 62 mm, 10 euro is 127 by 67 mm, 20 euro is 133 by 72 mm, and so on. Useful but check the denomination.

4. UK Pound Coin (1 GBP)

23.43 mm diameter. The 12-sided UK pound coin. UK 1p coin equals 20.3 mm, 2p coin 25.9 mm, 5p coin 18 mm, 10p coin 24.5 mm.

5. US Quarter

24.26 mm (0.955 inch) diameter. The US quarter is so close to 24 mm that it is a handy "about 1 inch" reference. A penny is 19.05 mm, nickel is 21.21 mm, dime is 17.91 mm.

6. A4 Paper

210 by 297 mm (8.27 by 11.69 inches). The international standard everywhere except North America. Folded in half it becomes A5 (148 by 210 mm); in half again it becomes A6 (105 by 148 mm). Every fold halves the larger dimension.

7. US Letter Paper

215.9 by 279.4 mm (8.5 by 11 inches). Standard in North America. Slightly wider but shorter than A4.

8. AA Battery

50.5 mm tall by 14.5 mm diameter. AAA is 44.5 by 10.5 mm. Useful for measuring slots, gaps, and small objects.

9. Standard Pencil (New, Unsharpened)

190 mm (7.5 inches) long. A brand-new wooden pencil is consistent worldwide. A US-style number 2 pencil is 7.5 inches; a European HB pencil is typically 175 to 190 mm.

10. iPhone or Smartphone

Each iPhone model has slightly different dimensions. Recent reference points:

• iPhone 15: 147.6 by 71.6 mm
• iPhone 15 Pro Max: 159.9 by 76.7 mm
• iPhone SE (3rd gen): 138.4 by 67.3 mm

If you know your phone model, its exact dimensions are easy to look up.

Using Body Parts as Rulers

For rough measurements when no objects are available, use your body, but measure your own body parts first so you know your personal numbers.

• Hand span (thumb tip to pinky tip, fingers spread): roughly 200 to 230 mm for adults.
• Finger width (index finger, middle joint): roughly 20 mm.
• Thumb-tip to first knuckle: roughly 25 mm (1 inch). This is literally where the inch originated.
• Elbow to fingertip (cubit): roughly 450 to 500 mm for adults.
• Average shoe size 9 US: 270 mm long.

The Best Solution: Calibrate an Online Ruler

Once you have used one of the items above to verify your screen, you can switch to our free online ruler for any measurement up to 50 cm. The credit-card calibration takes 10 seconds and stays saved on your device.