Resistor values are written in a few different shorthand styles. Once you know the rules, a schematic, a BOM and the tiny print on an SMD part all say the same thing.
The letter replaces the decimal point
On schematics and BOMs, the multiplier letter is placed where the decimal point would be. This stops a faint or missing dot from changing the value by a factor of ten.
| Written | Means |
|---|---|
4R7 | 4.7 Ω |
R47 | 0.47 Ω |
47R | 47 Ω |
4k7 | 4.7 kΩ (4,700 Ω) |
47k | 47 kΩ |
1M0 | 1.0 MΩ |
2M2 | 2.2 MΩ |
R means ohms, k means thousands and M means millions.
Three-digit and four-digit SMD codes
Chip resistors are too small for letters and units, so they use a number code.
- Three digits (5% parts): the first two digits are the value, the third is the number of zeros.
103is 10 followed by 3 zeros = 10,000 Ω = 10 kΩ.472= 4.7 kΩ.220= 22 Ω (not 220 Ω). - Four digits (1% parts): the first three digits are the value, the fourth is the number of zeros.
1002= 10 kΩ.4701= 4.7 kΩ. - Values under 10 Ω use R as the decimal point:
4R7= 4.7 Ω,0R1= 0.1 Ω. 0or000is a zero-ohm link, used as a jumper.
Very small 1% parts (0603 and below) sometimes use the EIA-96 code instead: two digits that index a table, plus a letter multiplier. If a marking doesn't make sense with the rules above, check an EIA-96 table.
Why you can't buy a 5 kΩ resistor everywhere
Resistors are made in standard "preferred value" series, spaced so that each value's tolerance band just meets the next one.
- E12 (10%): 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82
- E24 (5%): adds values in between, such as 11, 13, 16, 20, 24, 30, 36, 43, 51, 62, 75, 91
- E96 (1%): 96 values per decade, such as 10.0, 10.2, 10.5, 10.7, 11.0 …
That is why you see 4.7 kΩ and 5.1 kΩ far more often than 5 kΩ. If your calculation gives an odd number, pick the nearest value in the series you're using.
What else to specify
A value alone isn't a complete part. For a chip resistor, also decide:
- Package: 0402, 0603, 0805, 1206 — see our SMD package size guide.
- Tolerance: 1% is the sensible default for SMD; it costs almost the same as 5%.
- Power rating: check that I² × R in your circuit is comfortably below the part's rating.
Searching by value
Our search understands this notation. Typing 4k7, 4.7k or 4700 finds the same parts, and 10k 0805 narrows it to 10 kΩ in an 0805 package. You can also open Resistors and filter by resistance, tolerance and package.