🚧 Resistance

Resistance Converter

Reading resistor codes, checking a heating element, sizing a pull-up — convert ohms at any scale. Enter a value, choose units and press Convert.

Written and reviewed by SM Arijul Islam · Last reviewed 28 October 2026 · Editorial standards · Report an error

About the resistance converter

Resistance measures how strongly a material opposes electric current, one ohm being one volt per ampere. Electronic components usually sit in the kilo-ohm range, while insulation is measured in mega-ohms or giga-ohms.

Factors and formulas

1 Ω = 1,000 mΩ = 1,000,000 µΩ
1 kΩ = 1,000 Ω · 1 MΩ = 10⁶ Ω · 1 GΩ = 10⁹ Ω
1 abohm = 10⁻⁹ Ω
Ohm's law: R = V ÷ I
Resistors in series add; in parallel the reciprocals add

Most multimeters show an overload symbol ("OL") when the resistance is above their range — try a higher ohm setting.

How to convert electrical resistance

Resistance measures how strongly a component opposes the flow of current, in ohms (Ω). One ohm allows one ampere to flow when one volt is applied, which is Ohm's law: voltage equals current multiplied by resistance. Values span an enormous range, from milliohms in high-current cables and shunts to megohms in insulation, so metric prefixes do most of the practical work.

Common electrical resistance conversions

One ohm expressed in other units of electrical resistance
Unit	1 ohm equals
Milliohm (mΩ)	1,000
Kilo-ohm (kΩ)	0.001
Mega-ohm (MΩ)	0.000001
Giga-ohm (GΩ)	0.000000001

Everyday uses

Reading resistor colour codes and datasheets
Checking cable runs and insulation
Sensor, thermistor and strain-gauge specs
Circuit design and voltage dividers
Fault finding and continuity testing

Frequently asked questions

How many ohms are in a kilohm?

1,000. A megohm is one million ohms, and a milliohm is one thousandth of an ohm.

What is Ohm's law?

Voltage equals current multiplied by resistance (V = I × R), so resistance is voltage divided by current.

Does resistance change with temperature?

It does. Thermistors are engineered to change predictably with heat, while ordinary resistors drift only slightly.

Where do milliohm values matter?

In high-current paths such as battery shunts, relay contacts and thick cable runs, where even small resistances cause losses.

More worked examples

Two 100 ohm resistors in parallel give 50 ohms.
A 220 ohm resistor with 5 V across it carries about 22.7 mA.
Three 10 ohm resistors in series give 30 ohms.
One kilohm is 1,000 ohms and one megohm is 1,000,000 ohms.

Quick reference

Common resistance calculations and their results
Situation	Result
1 kilohm	1,000 ohms
1 megohm	1,000,000 ohms
100 ohm + 100 ohm in series	200 ohms
100 ohm and 100 ohm in parallel	50 ohms
5 V across 1 kilohm	5 mA
9 V across 470 ohm	about 19.1 mA

Common mistakes to avoid

Adding parallel resistances directly. The reciprocal sum always gives a total smaller than the smallest resistor in the group.
Forgetting the shorthand for two equal resistors in parallel: the result is exactly half of one of them.
Mixing ohms and kilohms in the same calculation, which is a factor of 1,000 error.
Ignoring tolerance. A gold-band resistor is within 5 percent, so a 100 ohm part may really be 105 ohms.

Further questions

How do I calculate parallel resistance?

Add the reciprocals: one over R total equals one over R1 plus one over R2, and so on. Then invert the result.

What do the colour bands on a resistor mean?

The first two bands give the significant digits, the third gives the multiplier, and the fourth gives the tolerance.

Why does an LED circuit need a resistor?

To limit the current. An LED has very little resistance of its own and can draw enough current to destroy itself without a series resistor.

Sources and standards

The ohm is realised through the quantum Hall effect, with the von Klitzing constant fixed by the 2019 SI. NIST SP 811 sets out the derived-unit relationships used here, including the distinction between resistance and reactance.