Resistor Calculator
Decode a resistor's color bands into its resistance and tolerance, or combine multiple resistors in series or parallel to find the total resistance.
Results from this calculator are estimates provided for general informational purposes only, based on formulas, rates, and standards commonly accepted as of 2026. Figures may differ slightly from other calculators or professional sources due to rounding methods, differing assumptions, or regional regulations, and rules may change over time. Always consult a qualified professional — such as a financial advisor, healthcare provider, or other relevant specialist — before making decisions based on these results.
Resistance
1 kΩ
± 5% tolerance
Acceptable Range
950 Ω – 1.05 kΩ
Example
A 4-band resistor with Brown, Black, Red, Gold bands reads 1 kΩ ± 5%, meaning its actual resistance falls between 950 Ω and 1.05 kΩ.
Resistor diagram
What is a Resistor Calculator?
A resistor calculator has two common jobs: reading a resistor's printed color bands to determine its resistance and tolerance, and figuring out the total resistance when multiple resistors are wired together in series or parallel. Resistors are almost never printed with their value in text — instead, colored bands encode the value so it can be read regardless of the resistor's orientation or size.
This calculator handles both jobs: pick your band colors to decode a resistance value, or enter a list of known resistor values to compute their combined resistance.
How the Color Code Works
Each color represents a digit from 0-9. On a 4-band resistor, the first two bands are significant digits, the third is a multiplier (a power of 10), and the fourth is the tolerance. A 5-band resistor adds a third significant digit for finer precision before the multiplier and tolerance bands.
Gold and silver multiplier bands represent fractional multipliers (×0.1 and ×0.01), used on resistors under 10 ohms. The tolerance band tells you how far the actual resistance can vary from the printed value — gold (±5%) and silver (±10%) are common on cheaper resistors, while brown (±1%) and red (±2%) indicate tighter precision.
Series vs. Parallel Combination
Resistors in series simply add together, since current has to pass through each one in turn. Resistors in parallel combine differently, because current has multiple paths to take — the combined resistance is always less than the smallest individual resistor in the group.
Why Tolerance Matters
No resistor is manufactured to be exactly its printed value — tolerance describes the guaranteed range around that value. A 1,000 Ω resistor with 5% tolerance could measure anywhere from 950 Ω to 1,050 Ω and still be considered within spec. For circuits sensitive to exact resistance (like precision voltage dividers or filters), choosing tighter-tolerance resistors matters more than it does for general-purpose use like current-limiting or pull-up/pull-down resistors.
Example — Your Current Inputs
A 4-band resistor with Brown, Black, Red, Gold bands reads 1 kΩ ± 5%, meaning its actual resistance falls between 950 Ω and 1.05 kΩ.
Additional Example — Classic 4.7kΩ Resistor
A resistor with yellow, violet, red, and gold bands reads: yellow = 4, violet = 7, red = ×100 multiplier, giving (4 × 10 + 7) × 100 = 4,700 Ω, or 4.7 kΩ, with gold indicating ±5% tolerance — one of the most common resistor values in general electronics.
About These Parameters
- Number of Bands
- 4-band resistors are the most common in general-purpose electronics; 5-band resistors add a third significant digit for tighter-tolerance, more precise values.
- Digit Bands
- Read left to right starting from the band closest to one end of the resistor. Each color maps to a single digit 0-9, from black (0) through white (9).
- Multiplier Band
- A power-of-10 scaling factor applied to the significant digits. Gold and silver represent fractional multipliers used on very low resistance values.
- Tolerance Band
- The guaranteed accuracy of the resistor as a percentage of its printed value — the last band, usually gold, silver, brown, or red.
- Resistor Values (Combination Mode)
- The known resistance of each resistor you're combining, in ohms. Enter at least two values to compute a series or parallel total.
Frequently Asked Questions
Which end do I start reading the color bands from?
Start from the band closest to one edge of the resistor — the tolerance band (often gold or silver) is usually spaced slightly apart from the others, which helps you identify which end to read from.
Why is combined parallel resistance always smaller than each individual resistor?
Because adding a parallel path always gives current an easier route overall, which can only decrease total resistance — the combined value is always less than the smallest resistor in the group.
What's the difference between a 4-band and 5-band resistor?
A 5-band resistor has an extra significant-digit band, allowing more precise values and tighter tolerances (often ±1% or better), while 4-band resistors are typically ±5% or ±10% and sufficient for general-purpose use.
Can I mix series and parallel resistors in one circuit?
Yes — many circuits combine both. Work out each parallel group's combined resistance first, then add series resistances (including any parallel-group totals) together to get the overall circuit resistance.