Resistor Value Calculator
Resistance from band values and tolerance.
Reviewed by the Calculation Machine team · Updated 24 October 2026 · How we check our maths
Your values
ⓘ Live results
- Resistance
- 47 kΩ
- Tolerance range
- 44650 – 49350 Ω
- Exact value
- 47,000 Ω
- Tolerance
- 5%
Quick answer
On a 4-band resistor, the first two bands are digits, the third is a power-of-ten multiplier and the fourth is tolerance: R = (first digit × 10 + second digit) × 10^multiplier. Yellow (4), violet (7), orange (×10³), gold (±5%) reads 47 kΩ, so the real value lies between 44.65 kΩ and 49.35 kΩ.
What the Resistor Value calculator does
This calculator converts the color bands on a through-hole resistor into its resistance and tolerance range. Look up each band's color in the chart below, enter the number it stands for, and the tool returns the value in Ω, kΩ or MΩ along with the lowest and highest value the part can have within its tolerance.
It is handy when sorting a mixed bag of resistors, checking a part on a board you are repairing, or confirming you picked the right resistor before soldering. Colors can be hard to tell apart — brown, red and orange in particular — so if in doubt, measure the part with a multimeter out of circuit.
The tool reads standard 4-band resistors. For 5- and 6-band precision parts, see the section on reading extra bands below. Once you know the values, the series/parallel resistor calculator combines them, and the Ohm's law calculator tells you the current they pass.
The formula
R = (d₁ × 10 + d₂) × 10^m Range = R × (1 ± t ÷ 100)
| Symbol | Meaning | Unit |
|---|---|---|
| d₁, d₂ | First and second significant digits (0–9) from bands 1 and 2 | — |
| m | Multiplier exponent from band 3 (black 0 to white 9; gold −1, silver −2) | — |
| t | Tolerance from band 4 | % |
| R | Nominal resistance | Ω |
The color code and its tolerance letters are defined in IEC 60062, and the nominal values resistors come in follow the E-series in IEC 60063 (E12 for 10% parts, E24 for 5%). Because of those series, a valid 5% resistor always has digits from the E24 list: 10, 11, 12, 13, 15, 16, 18, 20, 22, 24, 27, 30, 33, 36, 39, 43, 47, 51, 56, 62, 68, 75, 82, 91. If your reading is not on the list, you are probably reading the resistor backwards.
Worked examples
Yellow, violet, orange, gold
A common pull-up resistor from a kit, read left to right with the gold band on the right.
Inputs
- First digit4
- Second digit7
- Multiplier power3
- Tolerance5 %
Result
- Resistance47 kΩ
- Tolerance range44650 – 49350 Ω
- Exact value47,000 Ω
- Tolerance5%
47 kΩ ±5%, so anything from 44.65 kΩ to 49.35 kΩ on a meter is in spec. 47 is an E24 value, which confirms the reading direction.
Brown, black, red, brown
A 1% tolerance resistor whose bands read brown (1), black (0), red (×100), brown (±1%).
Inputs
- First digit1
- Second digit0
- Multiplier power2
- Tolerance1 %
Result
- Resistance1 kΩ
- Tolerance range990 – 1010 Ω
- Exact value1,000 Ω
- Tolerance1%
1 kΩ ±1%, so 990–1,010 Ω. Precision parts like this usually have five bands; a four-band 1% part is less common but does exist.
Red, red, green, silver
An older 10% carbon resistor from a vintage radio with red (2), red (2), green (×10⁵) and silver (±10%) bands.
Inputs
- First digit2
- Second digit2
- Multiplier power5
- Tolerance10 %
Result
- Resistance2.2 MΩ
- Tolerance range1980000 – 2420000 Ω
- Exact value2,200,000 Ω
- Tolerance10%
2.2 MΩ ±10%, so 1.98–2.42 MΩ. Old carbon-composition resistors often drift above their tolerance with age, so measure before reusing them.
Resistor color code chart
Bands 1 and 2 use the digit column, band 3 the multiplier column and band 4 the tolerance column. Gold as a multiplier means ×0.1 (enter −1) and silver ×0.01 (enter −2); as tolerance bands, gold is ±5%, silver ±10% and no band ±20%.
| Color | Digit | Multiplier | Tolerance |
|---|---|---|---|
| Black | 0 | ×1 | — |
| Brown | 1 | ×10 | ±1% |
| Red | 2 | ×100 | ±2% |
| Orange | 3 | ×1,000 (1 k) | — |
| Yellow | 4 | ×10,000 (10 k) | — |
| Green | 5 | ×100,000 (100 k) | ±0.5% |
| Blue | 6 | ×1,000,000 (1 M) | ±0.25% |
| Violet | 7 | ×10 M | ±0.1% |
| Grey | 8 | ×100 M | ±0.05% |
| White | 9 | ×1 G | — |
Which end to start reading from
- The tolerance band (often gold or silver) is usually set slightly apart from the others; start at the opposite end.
- Gold and silver never appear as the first band, so if one end is gold, read from the other.
- Bands are often bunched toward one end of the body; start at that end.
- If you get a value that is not a standard E-series number, flip the resistor and try again.
- Check the result with a meter when colors are ambiguous — heat-darkened or faded bands are common on old boards.
5-band and 6-band resistors and SMD codes
Precision resistors use three digit bands before the multiplier: brown, black, black, brown, brown reads 100 × 10 = 1 kΩ ±1%. To use this calculator, drop a trailing zero digit and add one to the multiplier — enter 1, 0 and multiplier 2. A sixth band, when present, gives the temperature coefficient in ppm/°C.
Surface-mount resistors print numbers instead of colors. A three-digit code is two digits plus a multiplier (472 = 47 × 10² = 4.7 kΩ); a four-digit code is three digits plus a multiplier (1002 = 10 kΩ); R marks the decimal point (4R7 = 4.7 Ω). If you are choosing a resistor for an LED, the LED resistor calculator gives the value to look for.
How to use the Resistor Value Calculator
- 1Hold the resistor with the tolerance band (usually gold or silver) on the right.
- 2Enter the digits for the first two bands using the chart — for example yellow = 4, violet = 7.
- 3Enter the third band as a power of ten: orange = 3, red = 2, gold = −1, silver = −2.
- 4Enter the tolerance from the last band (gold 5, silver 10, brown 1) and read the value and range.
Frequently asked questions
What are the colors for a 10k resistor?
Brown, black, orange: 1, 0 and ×1,000, followed by a tolerance band such as gold. On a 5-band resistor it is brown, black, black, red.
What color code is a 220 ohm resistor?
Red, red, brown: 2, 2 and ×10. With a gold fourth band it is 220 Ω ±5%.
What does a gold band mean on a resistor?
In the tolerance position it means ±5%. In the multiplier position (third band of four) it means ×0.1, so red, red, gold is 2.2 Ω.
What does no tolerance band mean?
A resistor with only three bands has a tolerance of ±20%. These are mostly found in old equipment.
How do I remember the resistor color code?
Learn the order black, brown, red, orange, yellow, green, blue, violet, grey, white for 0 to 9. Red to violet follows the rainbow, which helps.
References
- IEC 60062: Marking codes for resistors and capacitors — International Electrotechnical Commission (IEC)
- IEC 60063: Preferred number series for resistors and capacitors — International Electrotechnical Commission (IEC)
About this calculator
- Built and reviewed by the Calculation Machine team · How we build and test calculators
- Last reviewed: October 24, 2026
- Report an error