This calculator converts the three-digit codes found on surface mount resistors into their resistance value.
Resistance =
How the code works
Surface mount resistors are too small for colour bands, so most use a three-digit number printed on the body instead. You read it like this:
The first two digits are the significant figures — the value before you apply any multiplier. In the code 473, that is 47.
The third digit is the multiplier: the number of zeros to add, or the power of ten to multiply by. In 473, the 3 means multiply 47 by 10³, which is 1,000.
So 473 works out as 47 × 1,000 = 47,000 Ω, or 47 kΩ.
A few more examples:
- 104: This means 10 x 104 = 100,000 ohms (100 kOhms).
- 220: This means 22 x 100 = 22 ohms.
- 330: This means 33 x 100 = 33 ohms.
- 471: This means 47 x 101 = 470 ohms.
A trailing zero is a multiplier of one, not an extra zero on the end, which is why 220 is 22 Ω rather than 220 Ω. Values below 10 Ω use an R in place of the decimal point, 4R7 means 4.7 Ω, but those fall outside the plain three-digit scheme above.
