K
Krypton's Tools Free
Interactive SVG Simulator • Bidirectional Calculation

Resistor Color Code Calculator

Calculate resistance from color bands (3, 4, 5, and 6 bands), reverse calculate color bands from ohms, and decode SMD resistor codes with commercial E-series matching.

Loading resistor calculator...

Frequently Asked Questions

Everything you need to know about this tool

To read a 4-band resistor: the 1st band is the first significant digit, the 2nd band is the second significant digit, the 3rd band is the multiplier (power of 10), and the 4th band is the tolerance percentage (typically Gold for ±5% or Silver for ±10%). For example, Yellow (4) - Violet (7) - Red (×100) - Gold (±5%) equals 4,700 Ω or 4.7 kΩ ±5%.

A 4-band resistor has 2 significant digits and is typically used for standard ±5% or ±10% carbon film resistors. A 5-band resistor provides 3 significant digits for higher precision (±1% or ±0.5% metal film resistors). The 4th band in a 5-band resistor is the multiplier, and the 5th band is the tolerance.

The 6th band indicates the Temperature Coefficient of Resistance (TCR), measured in parts per million per Kelvin (ppm/K). It specifies how much the resistance drifts as temperature changes. Common TCR colors include Brown (100 ppm/K), Red (50 ppm/K), and Orange (15 ppm/K).

Our reverse resistor calculator lets you enter a target resistance value (such as 4.7 kΩ or 220 Ω) and instantly renders the exact color bands onto the interactive SVG resistor graphic. It also identifies the nearest standard commercial E12 and E24 decade values.

SMD (Surface Mount Device) resistors use printed numbers: in a 3-digit code (e.g. 472), the first 2 numbers are digits and the 3rd is the number of zeros (47 × 10² = 4.7 kΩ). In a 4-digit code (e.g. 4702), the first 3 numbers are digits and the 4th is the multiplier (470 × 10² = 47 kΩ). The letter 'R' represents a decimal point (e.g. 4R7 = 4.7 Ω).

EIA-96 is a 3-character alphanumeric system used for 1% precision SMD resistors. The first two digits (01 to 96) reference a 3-digit significant value lookup table, and the third letter (such as Y, X, A, B) represents the multiplier power.

Resistors are commercially manufactured in standard logarithmic value series specified by the EIA. E12 offers 12 steps per decade (10% tolerance), while E24 offers 24 steps per decade (5% tolerance). Our tool displays the closest matching commercial E-series part for your calculated resistance.