Electrical Resistance Unit Converter
Convert electrical resistance between milliohms (mΩ), ohms (Ω), kilohms (kΩ), megohms (MΩ) and gigohms (GΩ). Enter a value, pick the source and target units, and get an instant, step-by-step conversion.
Convert Resistance Between Ohms, Kilohms and Megohms
Resistance Unit Conversion Formula
Where:
- \(R_{\text{source}}\) — the resistance value you entered, in its original unit
- \(f_{\text{source}}\) — the SI multiplier of the source unit (e.g. \(10^3\) for kΩ)
- \(f_{\text{target}}\) — the SI multiplier of the target unit (e.g. \(1\) for Ω)
The formula first converts the value into base units of ohms, then divides by the target unit's multiplier. Because each unit is a standard SI prefix applied to the ohm, every conversion reduces to multiplying by a power of ten.
Resistance Units – Calculation Example
Example: a resistor is marked as 4700 Ω and you want to express its resistance in kilohms.
\[ f_{\text{source}} = 1, \quad f_{\text{target}} = 10^3 \]
\[ R = 4700 \times \frac{1}{10^3} = 4.7\ \text{kΩ} \]
Result: 4700 Ω = 4.7 kΩ (equivalently, 0.0047 MΩ).
How to Use the Calculator
- Enter the resistance value in the Resistance (R) field (the default example is 4700).
- Choose the unit of that value from the From unit dropdown: mΩ, Ω, kΩ, MΩ or GΩ.
- Select the unit you want in the Convert To dropdown.
- Read the Converted Resistance result, along with the value expressed in plain ohms and a breakdown of the calculation in Calculation Details.
What Are Resistance Units?
Electrical resistance measures how strongly a component opposes the flow of electric current. The SI base unit is the ohm (Ω), defined as the resistance through which one volt drives one ampere of current: \(1\ \Omega = 1\ \text{V/A}\). This relationship is the familiar form of Ohm's law, \(R = V/I\), which links voltage, current and resistance in any circuit.
Real-world resistances span an enormous range — from less than a milliohm for a thick copper bus bar to gigohms in insulation materials and precision high-value resistors. To keep the numbers readable, engineers use the standard SI prefixes: milliohm (mΩ) for very small values, kilohm (kΩ) for thousands of ohms, megohm (MΩ) for millions, and gigohm (GΩ) for billions. A 4700 Ω resistor is more conveniently written as 4.7 kΩ, which is exactly how it appears on schematics and in component catalogues.
Because each unit differs from the ohm only by a power of ten, converting between them is a matter of shifting the decimal point. The calculator does this instantly and also shows the intermediate value in ohms, which is useful when checking datasheets, resistor colour codes, or measurement instrument readouts that always report in base units.
Conversion Table
| Unit | Symbol | In ohms (Ω) |
|---|---|---|
| Milliohm | mΩ | \(10^{-3}\) |
| Ohm | Ω | \(1\) |
| Kilohm | kΩ | \(10^{3}\) |
| Megohm | MΩ | \(10^{6}\) |
| Gigohm | GΩ | \(10^{9}\) |
Assumptions, Limitations and Tips
- The calculator accepts non-negative values only. Negative resistances do not exist as passive physical quantities, so an entry below zero is rejected.
- Only the five units shown are supported. Related quantities such as conductance (siemens), resistivity (Ω·m) or impedance involve different dimensions and cannot be converted with a simple prefix.
- Very large or very small results are displayed in scientific notation for readability; you can safely copy them into reports or spreadsheets.
- When reading resistor labels, note the shorthand convention: "4k7" means 4.7 kΩ and "1M" means 1 MΩ — convert carefully to avoid a factor-of-1000 error.
- For context in practical electronics, resistance combines with voltage and current through Ohm's law; if you also work with electrical power, our Power Units converter handles watts, kilowatts and related units. Battery specifications often pair resistance with capacity — see the mAh to Wh converter — and signal work may benefit from the Data Transfer Rate converter.
Frequently Asked Questions
How do I convert ohms to kilohms or megohms by hand?
Every resistance unit differs from the ohm by a power of ten, so you only shift the decimal point. To go from ohms to kilohms, divide by 1000 (move the decimal three places left); to megohms, divide by \(10^6\). Going the other way, multiply: 2.2 kΩ = 2200 Ω and 3.3 MΩ = 3,300,000 Ω. The calculator automates this and shows the intermediate value in plain ohms so you can verify your mental math.
How many milliohms are in one ohm?
One ohm equals 1000 milliohms, because the prefix "milli" means one thousandth (\(10^{-3}\)). So 0.047 Ω is the same as 47 mΩ, and 500 mΩ equals 0.5 Ω. Milliohm values are common when measuring very low resistances such as wire, shunt resistors, circuit-board traces, and battery internal resistance, where instruments like micro-ohmmeters or four-wire (Kelvin) measurement setups are used.
What is a typical resistance value in real circuits?
It depends entirely on the application. Current-limiting and pull-up resistors in digital electronics typically fall between 100 Ω and 100 kΩ. Heating elements measure a few ohms to tens of ohms. Insulation resistance is huge — often hundreds of megohms or gigohms — which is why insulation testers (meggers) report in MΩ. Sensor and precision components span from milliohms (shunts) to gigohms (electrometer circuits).
Can this converter handle micro-ohms or units like siemens?
No. Only mΩ, Ω, kΩ, MΩ and GΩ are supported. A micro-ohm (\(10^{-6}\) Ω) is used for extremely low resistances like bus-bar joints; to convert manually, remember 1 μΩ = 0.001 mΩ. Conductance, measured in siemens (S), is the reciprocal of resistance: \(G = 1/R\). Since 1 S = 1/Ω, it cannot be converted with a prefix — you must divide, not multiply by a power of ten.
Why do resistors say "4k7" or "10k" instead of a full number?
This shorthand replaces the decimal point with the unit prefix to avoid misreading small print: "4k7" means 4.7 kΩ (4700 Ω), "1M" means 1 MΩ, and "R47" means 0.47 Ω. A frequent mistake is confusing "k" with "M" — they differ by a factor of 1000. Always double-check the letter before converting, especially on schematic diagrams and component reels where the type is small.
How does temperature affect the resistance value I'm converting?
Real resistors change value with temperature. Metal-film and carbon resistors drift only slightly (tens to hundreds of ppm/°C), but copper coils and other conductors can change by roughly 0.4% per degree Celsius. The converted number is only exact at the stated reference temperature, usually 20 °C or 25 °C. For precision work, check the component's temperature coefficient in its datasheet.
How do I convert a resistor color code into these units?
Read the bands left to right: the first two (or three) bands give digits, the next band is the multiplier, and the last band is tolerance. For example, yellow-violet-red-gold is 4-7-×100 = 4700 Ω = 4.7 kΩ, ±5%. Once you have the value in ohms, this converter restates it in any prefix unit you prefer, which is handy when a datasheet or schematic uses different units than the color code gives you.