Resistor Color Code Calculator
Pick the four band colours and read out the resistance in ohms, kilo-ohms or mega-ohms — with the tolerance min/max range — using the IEC 60062 colour code.
Resistance
47 kΩ ±5%
- Nominal value
- 47,000 Ω
- Two-digit base
- 47
- Multiplier
- × 1,000
- Tolerance
- ±5% (2.35 kΩ)
- Minimum (R − tol)
- 44.65 kΩ
- Maximum (R + tol)
- 49.35 kΩ
Read the resistor with the tolerance band (typically gold or silver) on the right. Bands 1–2 give the significant digits, band 3 the power-of-ten multiplier, band 4 the tolerance. R = (10·d₁ + d₂) × multiplier.
How to use this calculator
Hold the resistor with the tolerance band (almost always gold or silver, and usually offset further from the others) on the right. Read the remaining bands left-to-right and pick them in the dropdowns: band 1 is the first significant digit (0–9), band 2 is the second significant digit, band 3 is the power-of-ten multiplier, band 4 is the tolerance percentage. The calculator returns the nominal resistance in engineering notation (Ω, kΩ, MΩ, GΩ) plus the ± range, which is the band that real resistors are guaranteed to fall inside. If you cannot tell which end is the tolerance band, look for the gold/silver band — those colours never appear in bands 1 or 2 — or measure the gap: the tolerance band is usually printed slightly further from band 3 than the others are from each other.
How the calculation works
The four-band scheme is defined by IEC 60062 (and the older EIA RS-279) and is the same world-wide. The first two bands are digits 0–9: black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, gray 8, white 9 — the same order as the visible-light spectrum, with black and white as bookends. The third band is the decimal multiplier: black ×1, brown ×10, red ×100, orange ×1 000, yellow ×10 000, green ×100 000, blue ×1 M, violet ×10 M, gray ×100 M, white ×1 G, plus two negative-power colours used on sub-ohm resistors — gold ×0.1 and silver ×0.01. The fourth band is the tolerance: brown ±1%, red ±2%, green ±0.5%, blue ±0.25%, violet ±0.1%, gray ±0.05%, gold ±5%, silver ±10%, no band ±20%. The arithmetic is R = (10·d₁ + d₂) × multiplier in ohms, and the actual resistor is guaranteed to measure within R·(1 ± tol/100). All resistors are then drawn from one of the standardised E-series of preferred values (E6, E12, E24, E48, E96, E192) so that the tolerance bands tile the decade without gaps.
Worked example
A resistor banded yellow / violet / orange / gold reads digits 4 and 7 (yellow=4, violet=7), multiplier ×1 000 (orange), tolerance ±5% (gold). So R = 47 × 1 000 = 47 000 Ω = 47 kΩ ±5%. The acceptable range is 47 000 × (1 ± 0.05) = 44 650 Ω to 49 350 Ω — any measured resistance between 44.65 kΩ and 49.35 kΩ is in-spec. A 47 kΩ ±5% part lives in the E24 series, which is why you find it on the parts-bin row right next to 43 kΩ and 51 kΩ. Two more sanity-checks: brown-black-red-gold = 10 × 100 = 1 000 Ω = 1 kΩ ±5%, and brown-black-black-gold = 10 × 1 = 10 Ω ±5% (a low-value resistor; the multiplier black ×1 catches a lot of people out because black is also the zero in bands 1 and 2).
Frequently asked questions
Which end of the resistor do I read first?
Start from the end opposite the tolerance band. The tolerance band is almost always gold or silver, and is usually printed slightly further away from band 3 than bands 1–3 are spaced from each other. If both ends look similar — for example a precision resistor with a brown tolerance band — measure with a multimeter or check the parts list to break the tie. Reading the resistor backwards is the single most common mistake; a yellow-violet-orange-gold (47 kΩ ±5%) read backwards becomes gold-orange-violet-yellow, which is not a valid colour code at all (gold cannot be a digit band) — that is your hint to flip it.
Why do black and gold both look like multipliers?
Because they are — but they cover different parts of the range. Black is the ×1 multiplier (so a 10 Ω resistor is brown-black-black-tol, with black appearing as both the second digit and the multiplier), brown ×10, red ×100, and so on up to white ×1 G. Gold and silver were added later as fractional multipliers — gold ×0.1, silver ×0.01 — to mark sub-ohm and milli-ohm parts without needing an exponent system. Crucially, gold and silver never appear in bands 1 or 2 (they are not digits), which is why they double as the tolerance-end markers. If you see gold in the third position the resistor is sub-ohm; if you see it in the fourth it is the ±5% tolerance band.
What is the difference between 4-band, 5-band and 6-band resistors?
A 4-band resistor uses two digit bands, one multiplier and one tolerance — the form this calculator decodes. 5-band resistors use three digit bands instead of two, giving three-figure precision (typically with ±1% or ±2% tolerance) — a 5-band yellow-violet-black-red-brown reads 470 × 100 = 47 kΩ ±1%. 6-band resistors add a temperature-coefficient band on the end, in parts-per-million per kelvin (brown 100 ppm, red 50 ppm, etc.) — important when the resistor sits in a precision reference or an oven-controlled oscillator. Most through-hole parts in a hobbyist kit are 4-band ±5% (gold) or ±10% (silver). Surface-mount resistors do not use colour codes at all — they use numerical SMD codes (4-digit, 3-digit, or EIA-96).
Are these colour code rules different in the UK, US or anywhere else?
No — IEC 60062 is an international standard, adopted as BS EN 60062 in the UK, EIA RS-279 in the US and equivalent national variants elsewhere. The colour mapping, multipliers and tolerance values are identical world-wide. A 47 kΩ ±5% resistor coded yellow-violet-orange-gold in Tokyo, London, Lagos or San Francisco is the same part. The only regional variation worth knowing is that some older British and military codes used different tolerance colours (e.g. salmon for ±5%), but those have been obsolete since the 1970s.
What does ±5% tolerance actually mean for a real resistor?
It guarantees the manufacturer that the actual measured resistance is within ±5% of the printed nominal value. A 47 kΩ ±5% resistor is allowed to be anywhere between 44 650 Ω and 49 350 Ω at the reference temperature, and the manufacturer is not required to bin them more tightly — a batch can be drawn from anywhere in that band. The narrower the tolerance, the more expensive the resistor: ±20% is essentially free, ±5% costs almost nothing in carbon film, ±1% metal film is a small premium, and ±0.1% precision thin-film parts cost orders of magnitude more. For most digital and analogue work ±5% is fine; for current sensing, gain-setting, voltage references or filter cut-offs you usually want ±1% or better.
Why are some resistance values so common — 10 Ω, 4.7 kΩ, 47 kΩ — and others impossible to find?
Because resistors are manufactured in standardised E-series of preferred values, chosen so that the tolerance bands tile each decade with no gaps. E12 (used for ±10%) has 12 values per decade: 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82. E24 (±5%) has 24 values per decade, E96 (±1%) has 96. So you can buy 47 kΩ off the shelf because it sits at the E12 grid point, but 50 kΩ is not a stock value — you build it from a 47 kΩ + 3 kΩ pair, or use a trimmer. The series are geometric: each value is roughly the previous one × 10^(1/N) where N is the number per decade, which is why the spacing looks unfamiliar at first but is actually proportional to tolerance.