Resistor Colour Code Calculator: Four-Band and Five-Band Resistor Value and Tolerance

Read a resistor or find the colours of the bands for a value.

Calculated from standard textbook formulas, with every step shown. The formulas are fixed, so the working does not need checking: what matters is the numbers you type in. Use these calculators only if you are competent to choose the inputs (loads, material strength, dimensions, supports) and check your units and assumptions. For learning and checking your own working: design and sign-off are for a qualified engineer. Drafting Central does not store the numbers you type.

How this calculator works

Choose four or five bands and pick the colour of each band, starting from the end of the resistor with the bands close together.

The calculator gives the digits, the multiplier, the resistance in ohms, kilohms or megohms and the range allowed by the tolerance.

To go the other way, enter a resistance and it gives the colours of the bands.

Formulas used

  • R = (10d_1 + d_2)\times10^{m}
  • R = (100d_1 + 10d_2 + d_3)\times10^{m}

Worked example

With the default numbers in the calculator above:

  1. The digits: 10
  2. The multiplier: Times ten to the power 2
  3. Resistance: 1000.00 ohm (1.00 kohm)
  4. Tolerance and the range the real value may lie in: 950.00 to 1050.00 ohm (plus or minus 5 percent)

Change the numbers in the calculator to see the full working, every step, for your own case.

A second worked example

A different case, with these numbers: What do you want? Find the colours for a value.

  1. The digits and the multiplier for this value: 47 times ten to the power 2
  2. Colours of the bands, from the one nearest the end of the resistor: Yellow, violet, red. Then add a tolerance band: gold for 5 percent, silver for 10 percent

Common questions

Which end do I read from?

The end with the bands closest together. The tolerance band is set slightly apart.

What do the colours mean?

Black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, grey 8, white 9. Gold and silver as multipliers are 0.1 and 0.01.

What do gold and silver tolerance bands mean?

Gold is 5 percent and silver is 10 percent.

Why use five bands?

A fifth band adds a third digit, for resistors with a tolerance of 1 percent or better.

Related calculators

Got a question about this? Ask an engineering question and get a plain-language answer with references.

Further reading: IEC 60062 Marking codes for resistors and capacitors.

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