4‑Band Resistor Color Code Calculator

4‑Band Resistor Calculator

Select the colors to determine the resistor’s value and tolerance.

Select the colors to see the resistance value.
4-Band Resistor Color Code

4-Band Resistor Color Code

Resistors are electronic components that limit or regulate the flow of electrical current in a circuit. A common way to specify a resistor’s value is by using color bands. In a 4-band resistor, these colored rings indicate the resistor’s value (in ohms), along with the tolerance, describing how accurate that value is expected to be.

Color Code Basics

The 4-band code is read from one end of the resistor to the other. Usually, the first band is the one closest to a lead (the metallic wire extending from the resistor’s body) or is visually separated from the rest. The four color bands have the following meaning:

  • 1st Band: First digit of the resistor value
  • 2nd Band: Second digit of the resistor value
  • 3rd Band: Multiplier (the power of 10 factor)
  • 4th Band: Tolerance (e.g., ±5%, ±10%, etc.)

Each color corresponds to a specific digit or multiplier. The digits 0–9 are assigned standardized colors (e.g., black = 0, brown = 1, red = 2, and so on). Tolerances are indicated by certain colors like gold (±5%), silver (±10%), or no band (±20%).

Color Code Table

Below is a general reference for the color-to-digit and color-to-multiplier assignments. Note that some manufacturers might have slight variations, but these are the most commonly accepted standards.

Color Digit Multiplier Tolerance
Black 0 × 100 N/A
Brown 1 × 101 ±1%
Red 2 × 102 ±2%
Orange 3 × 103 N/A
Yellow 4 × 104 N/A
Green 5 × 105 ±0.5%
Blue 6 × 106 ±0.25%
Violet (Purple) 7 × 107 ±0.1%
Gray 8 × 108 ±0.05%
White 9 × 109 N/A
Gold – × 10-1 ±5%
Silver – × 10-2 ±10%
No Band – – ±20%

Formula for Resistor Value

The value of a 4-band resistor in ohms (Ω) can be expressed as:

R = (10 × D1 + D2) × M
  • D1: Digit represented by the first band
  • D2: Digit represented by the second band
  • M: Multiplier represented by the third band

The fourth band indicates the tolerance. For example, a gold band typically means ±5% tolerance.

Example: Brown, Black, Red, Gold

Let’s decode a resistor with the color bands: Brown (1st) – Black (2nd) – Red (3rd) – Gold (4th).

  • D1 (Brown) = 1
  • D2 (Black) = 0
  • M (Red) = 102 = 100
  • Tolerance (Gold) = ±5%

Using the formula:

R = (10 × 1 + 0) × 100 = (10) × 100 = 1,000 Ω

So the resistor value is 1 kΩ (1000 ohms) with a tolerance of ±5%.

Example: Red, Violet, Orange, Silver

Suppose the color bands are Red (1st) – Violet (2nd) – Orange (3rd) – Silver (4th).

  • D1 (Red) = 2
  • D2 (Violet) = 7
  • M (Orange) = 103 = 1,000
  • Tolerance (Silver) = ±10%

Using the formula:

R = (10 × 2 + 7) × 1000 = 27 × 1000 = 27,000 Ω

So the resistor value is 27 kΩ (27,000 ohms) with a tolerance of ±10%.

Key Takeaways:
  • 4-band resistors show two digits, a multiplier, and a tolerance.
  • The first two color bands give the numeric digits, and the third band sets the multiplier.
  • The fourth band indicates tolerance—often ±5% for gold, ±10% for silver, and so on.
  • If unsure which side is the first band, look for the side with a band closer to the resistor’s end, or the group of three consecutive bands that are spaced closer together.

Mastering the 4-band resistor color code helps in quickly identifying resistor values without needing additional equipment. Once you recognize the standard color-to-digit mappings and the multiplier roles, reading resistor values becomes second nature in electronics work.