Answer first
What this calculator tells you
Read a four-band resistor's value and tolerance range from its color bands. Identify a resistor from its bands before you put it in a circuit. Formula: Resistance = (first digit × 10 + second digit) × multiplier; tolerance sets the minimum and maximum. At the worked-example inputs, the resistance (ohms) is 1,000. Holding every other input steady, moving first band from -1 to 3 moves the result from -1,000 to 3,000.
Transparent method
The formula
Identify a resistor from its bands before you put it in a circuit.
Worked example
Example inputs
How to interpret the result
Four colored bands encode a resistor's value: two digits, a multiplier and a tolerance. Brown, black and red read as 1, 0 and times 100, which is 1,000 ohms, and a gold band adds a 5 percent tolerance, so the real value may land between 950 and 1,050. Hold the resistor with the tolerance band at the right, since the bands read from the end away from it.
At the worked-example inputs the resistance (ohms) is 1,000. It rises with first band and second band and falls as multiplier band increases.
These are exact physics and chemistry formulas. Real-world results add tolerances from component quality, temperature and measurement error that this calculator does not model.
Before you rely on it
What to check
Measure with a multimeter when it matters. Bands can fade, and some colors look alike in poor light.
The common error
Where people go wrong with resistor color code calculator
Reading the bands from the wrong end. The tolerance band, usually gold or silver, goes on the right, and reading backward gives a different value.
Sensitivity evidence
How first band changes the resistance (ohms)
Holding every other input at the worked-example value, moving first band from -1 to 3 moves the resistance (ohms) from -1,000 to 3,000: a spread of 4,000, or 400% of the worked-example result.
| First band | Resistance (ohms) | Minimum (ohms) | Maximum (ohms) |
|---|---|---|---|
| -1 | -1,000 | -950 | -1,050 |
| 0 | 0 | 0 | 0 |
| 1worked example | 1,000 | 950 | 1,050 |
| 2 | 2,000 | 1,900 | 2,100 |
| 3 | 3,000 | 2,850 | 3,150 |
Every input, tested
Which input moves the resistance (ohms) most
Of the 3 inputs, first band moves the resistance (ohms) most (9,000 across the range tested) and second band moves it least (900).
| Input | Tested from | To | Resistance (ohms) at each end | Swing |
|---|---|---|---|---|
| First band | Black (0) | White (9) | 0 to 9,000 | 9,000 (500%) |
| Multiplier band | Black (×1) | Silver (×0.01) | 10 to 0.1 | 9.9 (99999%) |
| Second band | Black (0) | White (9) | 1,000 to 1,900 | 900 (50%) |
Step by step
The worked example, input by input
| Input | Value used | What it means |
|---|---|---|
| First band | Brown (1) | The first significant digit. |
| Second band | Black (0) | The second significant digit. |
| Multiplier band | Red (×100) | The power of ten applied to the two digits. |
| Tolerance band | Gold (±5%) | How far the real value may differ. |
| Resistance (ohms) | 1,000 | |
| Minimum (ohms) | 950 | |
| Maximum (ohms) | 1,050 | |
Inputs, definitions and assumptions
First band
The first significant digit. The prefilled worked-example value is Brown (1).
Second band
The second significant digit. The prefilled worked-example value is Black (0).
Multiplier band
The power of ten applied to the two digits. The prefilled worked-example value is Red (×100).
Tolerance band
How far the real value may differ. The prefilled worked-example value is Gold (±5%).
How to use this calculator
- 1Verify the inputs. Gather first band, second band, multiplier band and tolerance band from your own documents; the prefilled values are examples.
- 2Save a baseline. The worked example puts the resistance (ohms) at 1,000. Store your own version of it as Scenario A.
- 3Test one change. Start with first band, the input with the biggest effect here: switching first band changes the resistance (ohms): black (0) gives 0; brown (1) gives 1,000; red (2) gives 2,000; orange (3) gives 3,000; yellow (4) gives 4,000; green (5) gives 5,000.
- 4Check the boundary. Read the interpretation boundary above before acting on the result.
People also ask
Frequently asked questions
How do you calculate resistor color code?
Resistance = (first digit × 10 + second digit) × multiplier; tolerance sets the minimum and maximum. At the worked-example inputs the resistance (ohms) is 1,000.
What does the resistor color code result mean?
Identify a resistor from its bands before you put it in a circuit. At the worked-example inputs the resistance (ohms) is 1,000. It rises with first band and second band and falls as multiplier band increases.
How much does first band change the resistance (ohms)?
Holding every other input at the worked-example value, moving first band from -1 to 3 moves the resistance (ohms) from -1,000 to 3,000, a spread of 4,000.
What are the limits of this resistor color code calculator?
These are exact physics and chemistry formulas. Real-world results add tolerances from component quality, temperature and measurement error that this calculator does not model. The tables on this page test first band only from -1 to 3; a value outside that range is not tabulated here.
Which input moves the resistance (ohms) most in the resistor color code calculator?
Ranked by how far each moves the resistance (ohms) across the range tested: first band (9,000, 500%), multiplier band (9.9, 99999%) and second band (900, 50%).
How much does second band matter in the resistor color code calculator?
The worked example uses Black (0). With the other inputs left at the worked example, switching second band changes the resistance (ohms): black (0) gives 1,000; brown (1) gives 1,100; red (2) gives 1,200; orange (3) gives 1,300; yellow (4) gives 1,400; green (5) gives 1,500.
How much does multiplier band matter in the resistor color code calculator?
The worked example uses Red (×100). With the other inputs left at the worked example, switching multiplier band changes the resistance (ohms): black (×1) gives 10; brown (×10) gives 100; red (×100) gives 1,000; orange (×1,000) gives 10,000; yellow (×10,000) gives 100,000; green (×100,000) gives 1,000,000.
Which inputs change the minimum (ohms) in the resistor color code calculator?
At the worked-example inputs it is 950. First band takes it from 0 to 8,550, second band takes it from 950 to 1,805 and multiplier band takes it from 9.5 to 0.095.
Which inputs change the maximum (ohms) in the resistor color code calculator?
At the worked-example inputs it is 1,050. First band takes it from 0 to 9,450, second band takes it from 1,050 to 1,995 and multiplier band takes it from 10.5 to 0.105.
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Sources and evidence
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