Resistor Values Calculator

If you’ve ever stared at a tiny resistor and wondered what those colored stripes mean, you’re not alone. A Resistor Values Calculator takes the guesswork out of reading color bands and returns the resistor’s nominal resistance, tolerance range, and—on 6-band parts—the temperature coefficient. This guide explains how the calculator works, the plain-text formulas it uses, step-by-step examples (with arithmetic shown digit-by-digit), helpful tips, and 20 FAQs.

Resistor Values Calculator

What the Resistor Values Calculator does

The calculator converts resistor color bands into:

  • Nominal resistance (ohms, kiloohms, megaohms)
  • Tolerance (percent), giving minimum and maximum resistance ranges
  • Multiplier (power-of-ten factor)
  • Temperature coefficient (ppm/°C) for 6-band resistors (optional)
    It supports standard 4-band, 5-band, and 6-band color codes and can also accept numeric values directly.

Color code basics (plain text)

Each color corresponds to a digit, multiplier, tolerance, and sometimes a temperature coefficient:

Digits (band 1, 2, and 3 for 5-band):
black=0, brown=1, red=2, orange=3, yellow=4, green=5, blue=6, violet=7, grey=8, white=9

Multipliers (×10^n):
black=×10^0, brown=×10^1, red=×10^2, orange=×10^3, yellow=×10^4, green=×10^5, blue=×10^6, violet=×10^7, grey=×10^8, white=×10^9, gold=×10^-1, silver=×10^-2

Tolerance:
brown=±1%, red=±2%, green=±0.5%, blue=±0.25%, violet=±0.1%, grey=±0.05%, gold=±5%, silver=±10%, none=±20%

Temperature coefficient (ppm/°C) — for 6-band resistors (examples):
brown=100 ppm/°C, red=50 ppm/°C, orange=15 ppm/°C, yellow=25 ppm/°C, blue=10 ppm/°C — (calculator includes lookup).

Plain-text formulas

  1. Nominal resistance (4-band):
    Value = ((Digit1 × 10) + Digit2) × Multiplier
  2. Nominal resistance (5-band):
    Value = ((Digit1 × 100) + (Digit2 × 10) + Digit3) × Multiplier
  3. Tolerance range:
    Min = Value × (1 − TolerancePct)
    Max = Value × (1 + TolerancePct)
  4. Display units: convert ohms to kΩ or MΩ when value ≥ 1,000 or ≥ 1,000,000.

How to use the Resistor Values Calculator

  1. Select band count — 4, 5, or 6 bands.
  2. Pick colors for each band (leftmost is band 1; read toward the tolerance band).
  3. Click Calculate — the result shows nominal resistance, tolerance, min/max, multiplier, and tempco (if provided).
  4. Optional: enter a measured resistance to see if it’s within tolerance.

Example 1 — 4-band resistor (step-by-step, digits shown)

Bands (left → right): yellow, violet, red, gold
Using the tables above:

  • Digit1 (yellow) = 4
  • Digit2 (violet) = 7
  • Multiplier (red) = ×10^2 = 100
  • Tolerance (gold) = ±5% = 0.05

Step 1 — Combine digits:
Digit1 × 10 = 4 × 10 = 40
Add Digit2: 40 + 7 = 47

Step 2 — Apply multiplier:
47 × 100 = 4,700

Nominal value: 4,700 ohms → display as 4.7 kΩ

Step 3 — Tolerance range:
Min = 4,700 × (1 − 0.05) = 4,700 × 0.95
Calculate: 4,700 × 0.95 = 4,465.00 → 4,465 Ω
Max = 4,700 × (1 + 0.05) = 4,700 × 1.05
Calculate: 4,700 × 1.05 = 4,935.00 → 4,935 Ω

Result: 4.7 kΩ ±5% → range 4,465 Ω – 4,935 Ω

Example 2 — 5-band resistor (step-by-step)

Bands: brown, black, black, brown, brown

  • Digit1 (brown) = 1
  • Digit2 (black) = 0
  • Digit3 (black) = 0
  • Multiplier (brown) = ×10 = 10
  • Tolerance (brown) = ±1% = 0.01

Step 1 — Combine digits:
Digit1 × 100 = 1 × 100 = 100
Digit2 × 10 = 0 × 10 = 0
Digit3 = 0
Sum = 100 + 0 + 0 = 100

Step 2 — Apply multiplier:
100 × 10 = 1,000

Nominal value: 1,000 Ω → 1.0 kΩ

Tolerance range:
Min = 1,000 × (1 − 0.01) = 1,000 × 0.99 = 990 Ω
Max = 1,000 × (1 + 0.01) = 1,000 × 1.01 = 1,010 Ω

Result: 1.0 kΩ ±1% → 990 Ω – 1,010 Ω

Example 3 — 6-band resistor (includes temperature coefficient)

Bands: brown, grey, black, orange, brown, brown

  • Digit1 (brown) = 1
  • Digit2 (grey) = 8
  • Digit3 (black) = 0
  • Multiplier (orange) = ×10^3 = 1,000
  • Tolerance (brown) = ±1%
  • Tempco (brown) = 100 ppm/°C

Step 1 — Combine digits:
1 × 100 = 100
8 × 10 = 80

  • 0 = 0
    Sum = 100 + 80 + 0 = 180

Step 2 — Apply multiplier:
180 × 1,000 = 180,000 → 180 kΩ

Tolerance: ±1% → Min = 180,000 × 0.99 = 178,200 Ω; Max = 180,000 × 1.01 = 181,800 Ω

Temperature coefficient: 100 ppm/°C means resistance changes by 100 parts per million per degree Celsius (0.01%/°C). For a 10°C rise: change = 180,000 × (100 × 10) / 1,000,000 = 180,000 × 0.001 = 180 Ω.

Helpful tips

  • Read bands from the end with the tolerance band (usually gold, silver, brown, or none) on the right. The side with the bands closer together is typically the left end.
  • 5-band resistors are more precise — used when tolerance is 1% or better.
  • If a band is faded or ambiguous, measure with a multimeter instead of guessing.
  • For SMD resistors, the marking may be numeric (e.g., 472 = 4.7 kΩ) or use a 3-digit/4-digit code; the calculator can accept numeric codes too.
  • Temperature coefficient matters in precision or temperature-sensitive circuits.

20 Frequently Asked Questions (FAQs)

  1. How do I know which end to start reading? Read from the end nearest the tolerance band (gold/silver/brown) or the side with a gap to the body.
  2. What’s the difference between 4-band and 5-band? 4-band uses two significant digits; 5-band uses three, giving finer resolution.
  3. What does gold multiplier mean? gold = ×10^-1 (divide by 10).
  4. What does no tolerance band mean? It usually means ±20% tolerance.
  5. How to read SMD resistors? Use numeric codes (e.g., 103 = 10 × 10^3 = 10 kΩ) or consult an SMD code table.
  6. Can a resistor be out of tolerance? Yes — aging or overheating can shift values beyond tolerance.
  7. What is ppm/°C? Parts per million per degree Celsius — indicates how temperature changes resistance.
  8. Do color codes differ for capacitors? Yes — don’t confuse component standards.
  9. What if the color looks brown-black? Lighting and paint can mislead — verify with a meter.
  10. Are there standard resistor series? Yes — E6, E12, E24, E48, E96 series define preferred values.
  11. How precise is a 1% resistor? Nominally within ±1% of stated value.
  12. Why are some bands metallic? Gold and silver indicate multiplier and tolerance, not digits.
  13. Can two resistors of same color code have different wattage? Yes — color code shows value/tolerance, not power rating.
  14. What if I have three bands only? That’s unusual; some old parts may have limited marking—measure them instead.
  15. Why do some resistors have 6 bands? For precision parts that include tempco.
  16. How to convert ohms to kΩ? Divide by 1,000. Example: 4,700 Ω → 4,700 ÷ 1,000 = 4.7 kΩ.
  17. What’s an easy trick to remember colors? Mnemonics exist (but be careful—remember modern inclusive variants).
  18. Can I use the calculator offline? Yes — a simple calculator with lookups does the job.
  19. Is color code universal? Largely yes—IEC standard color codes are widely used.
  20. Where to learn more? Electronics textbooks, component datasheets, and hands-on practice with a multimeter.