Resistance Calculator

Select Resistor Bands

Select bands to calculate
Tolerance: —
LIVE CIRCUIT DIAGRAM
RESISTOR VALUES
Total Resistance
—
Ω
SERIES CONNECTION
Resistors are connected end-to-end.
Same current flows through each resistor.
Total voltage = sum of voltages across each.
Rₜ = R₁ + R₂ + R₃ + …
PARALLEL CONNECTION
Resistors are connected side-by-side.
Same voltage appears across each resistor.
Total current = sum of currents through each.
1/Rₜ = 1/R₁ + 1/R₂ + 1/R₃ + …
Resistor Colour Code

Resistor Colour Code Calculator

This tool helps you quickly decode resistor colour bands to determine their resistance value and tolerance. It is widely used in Arduino, ESP32, robotics, and electronics prototyping.

Instead of manually calculating values, simply select the colours and get instant, accurate results for your circuit design.

How the Colour Code Works

  • 1st Band: First Digit
  • 2nd Band: Second Digit
  • 3rd Band: Multiplier
  • 4th Band: Tolerance

Example: Red – Violet – Yellow – Gold
= 270kΩ ±5%

Resistor Color Code

An electronic color code is used to specify the value and tolerance of resistors. Instead of printing numbers, resistors use colored bands to represent their resistance in Ohms (Ω). This standard is defined by IEC 60062 and is used worldwide.

How the Color Coding Works

Each band on a resistor represents a specific value based on its position. A typical resistor has, four bands read from left to right::

  • 1st Band: This is the First significant digit.
  • 2nd Band: This is the second significant digit.
  • 3rd Band: This is the multiplier, which tells you how many zeros to add to the digits, scaling the value by a power of ten.
  • 4th Band: his is the tolerance, which indicates the manufacturing precision. It shows the percentage by which the actual resistance may vary from its stated value.

The resistor is always read from left to right, with the tolerance band spaced slightly apart.

Example

Suppose the bands are Green, Red, Red, Gold:

  • 1st Digit (Green): 5
  • 2nd Digit (Red): 2
  • Multiplier (Red): 10^2
  • Tolerance (Gold): +- 5%

So the resistance value becomes:

52 × 10^2 = 5200 ohms ±5%

The resistor is rated at 5,200 Ω. However, because of the Gold tolerance band, it can measure anywhere between 4,940 Ω and 5,460 Ω, and still be considered “in spec.

Color Code Reference Table

Color Digit Multiplier Tolerance
Black0×1—
Brown1×10±1%
Red2×100±2%
Orange3×1K—
Yellow4×10K—
Green5×100K±0.5%
Blue6×1M±0.25%
Violet7×10M±0.1%
Grey8×100M±0.05%
White9×1G—
Gold—×0.1±5%
Silver—×0.01±10%

Resistors in Series

When resistors are connected end-to-end, they are said to be in series. The total resistance is simply the sum of all resistances.

Rtotal = R₁ + R₂ + R₃ + ... + Rn

Resistors in Parallel

When resistors are connected across the same two nodes, they are in parallel. The total resistance is found using the reciprocal formula.

1 / Rtotal = 1/R₁ + 1/R₂ + 1/R₃ + ... + 1/Rn

More Advanced Resistors

Precision resistors may have 5 or 6 bands:

  • 5-Band: Adds a third significant digit for higher accuracy
  • 6-Band: Includes temperature coefficient (ppm/K)

These are commonly used in measurement equipment, industrial electronics, and high-precision circuits.