Image:BluetoohUSB.JPG

This image has a coin in it to indicate scale.

Do not use object such as coins for scale, as they will require people unfamiliar with them to look up the dimensions or guess, both of which defeat the purpose of the object in the first place. Coins are particularly bad as they can reinforce a geographical bias.

Please photograph a ruler with the subject or add a scale marking via an image editor instead. SI/metric units are the most commonly used worldwide (see metre, 1 E-2 m).

Examples of good practice: with (metric & imperial) ruler and with superimposed line.
Examples of bad practice: here.

• U.S. and Canada:
  • 1¢: 19 mm, 0.75 in;
  • 5¢: 20 mm, 0.79 in;
  • 10¢: 18 mm, 0.71 in;
  • 25¢: 24 mm, 0.95 in;
  • 50¢: 30 mm, 1.18 in;
  • $1: 26 mm, 1.02 in;
  • $2: 28 mm, 1.10 in.

• UK
  • 1p: 20.32 mm, 0.80 in;
  • 2p: 25.91 mm, 1.02 in;
  • 5p: 18.00 mm, 0.71 in;
  • 10p: 24.50 mm, 0.96 in;
  • 20p: 21.40 mm, 0.84 in;
  • 50p: 27.30 mm, 1.07 in;
  • £1: 22.50 mm, 0.89 in;
  • £2: 28.40 mm, 1.12 in.

• Eur
  • 1¢: 16.25 mm,
  • 2¢: 18.75 mm,
  • 5¢: 21.25 mm,
  • 10¢: 19.75 mm,
  • 20¢: 22.25 mm,
  • 50¢: 24.25 mm,
  • 1€: 23.25 mm,
  • 2€: 25.75 mm,