How to use
- Read the marking on the component and enter only the code, such as 472, 1002 or 4R7. Uppercase and lowercase R are accepted.
- Press Calculate to see the resistance, the detected notation and a component diagram carrying your code. Copy result copies the code and all resistance units. Editing or clearing the code removes both the values and diagram.
Formula and interpretation
For a 3-digit numeric code, the first two digits are the significant value and the last digit is the power of ten. Four-digit codes use three significant digits. R replaces the decimal point and the resulting value is in ohms. Unit conversion uses 1 kΩ = 1,000 Ω and 1 MΩ = 1,000,000 Ω.
Worked example
472 means 47 × 10² = 4,700 Ω = 4.7 kΩ = 0.0047 MΩ. Code 1002 means 100 × 10² = 10,000 Ω. Code 4R7 gives 4.7 Ω, while R22 gives 0.22 Ω. Codes 000 and 0000 decode to zero ohms.
Limits and input errors
Supported R markings contain at least one digit and at most four characters in total, such as R22, 4R7, 10R0 or 100R. EIA-96 codes such as 01C are explicitly unsupported. Other letters, color bands and manufacturer-specific markings are not decoded. A printed code alone does not establish component type or condition.
Frequently asked questions
Does a 3-digit code tell me the tolerance?
No. This tool calculates the nominal value only. Determine tolerance, package size and power rating from the exact manufacturer data sheet.
Can I identify an unmarked or damaged resistor?
No. Do not guess missing digits. Use the circuit documentation or an appropriate measurement; in-circuit measurements can be affected by other components.