1
Ω
1,000
mΩ
0.001
kΩ
0.000001
MΩ
0.000000001
GΩ
1
Ω
1,000
mΩ
0.001
kΩ
0.000001
MΩ
0.000000001
GΩ
The Electric Resistance Conversion Calculator converts resistance values between ohms (Ω), milliohms (mΩ), kilohms (kΩ), megohms (MΩ), and gigohms (GΩ). Electrical resistance quantifies how strongly a material opposes the flow of electric current. Ohm's law relates resistance to voltage and current: $$R = \frac{V}{I}$$ One ohm is the resistance that produces one volt of potential difference when one ampere of current flows through it.
The metric prefix system spans the enormous range of practical resistances: $$1\ \text{G}\Omega = 10^{9}\ \Omega, \quad 1\ \text{M}\Omega = 10^{6}\ \Omega, \quad 1\ \text{k}\Omega = 10^{3}\ \Omega, \quad 1\ \text{m}\Omega = 10^{-3}\ \Omega$$
Milliohm resistances appear in high-current applications: PCB trace resistance (1–50 mΩ), current-sense shunt resistors (1–100 mΩ), contact resistance of switches and connectors, and wire resistance in power distribution. Ohm-range resistors are the workhorses of electronics — biasing networks, voltage dividers, current limiters, and termination resistors. Kilohm resistances dominate signal-level circuits: pull-up/pull-down resistors (1–100 kΩ), feedback networks in op-amp circuits, and RC timing circuits. Megohm values appear in high-impedance input circuits, leakage specifications, and insulation resistance of cables. Gigohm resistances characterize insulation testing (megger readings), PCB surface resistance in humid conditions, and ultra-high-impedance amplifier inputs.
Converting between resistance scales is essential in electronics design. A datasheet specifying 4.7 kΩ must be correctly interpreted as 4700 Ω when calculating current. Insulation resistance specifications in MΩ or GΩ must be compared against standards given in different units. Current-sense resistors rated in mΩ produce voltage drops that must be computed in volts or millivolts.
This calculator provides instant conversion across all five units, supporting engineers from power electronics (mΩ) through signal processing (kΩ) to insulation testing (GΩ).
The calculator normalizes the input to ohms (the SI unit), then converts to all target units:
Step 1 — Convert to Ohms:
$$R_{\Omega} = R_{\text{input}} \times 10^{n}$$
where n is the prefix exponent: GΩ (n = 9), MΩ (n = 6), kΩ (n = 3), Ω (n = 0), mΩ (n = −3).
Step 2 — Convert from Ohms to all units:
$$R_{\text{m}\Omega} = R_{\Omega} \times 10^{3}, \quad R_{\text{k}\Omega} = R_{\Omega} \times 10^{-3}$$
$$R_{\text{M}\Omega} = R_{\Omega} \times 10^{-6}, \quad R_{\text{G}\Omega} = R_{\Omega} \times 10^{-9}$$
All conversions are exact powers of ten with no rounding error.
All outputs represent the same physical resistance in different scales. Use milliohms for high-current paths — shunt resistors, bus bars, contact resistance measurements. Use ohms for general circuit components and Ohm's law calculations at standard current levels. Use kilohms for signal conditioning, biasing, and filter design. Use megohms for insulation quality assessment, high-impedance inputs, and leakage specifications. Use gigohms for insulation testing (hipot/megger), surface resistance in clean rooms, and electrostatic discharge characterization. When reading color codes on resistors, the multiplier band directly gives the order of magnitude in ohms.
Inputs
Results
A 10 mΩ current-sense resistor equals 0.01 Ω. At 5 A, it produces V = IR = 5 × 0.01 = 50 mV, which a current-sense amplifier can measure. Power dissipation is I²R = 25 × 0.01 = 0.25 W.
Inputs
Results
A cable insulation reading of 2.5 GΩ equals 2500 MΩ — well above the typical 1 MΩ-per-kV minimum standard. This indicates excellent insulation with negligible leakage current at operating voltages.
Resistance depends on material resistivity (ρ), length (L), and cross-sectional area (A): R = ρL/A. Copper has ρ ≈ 1.68 × 10⁻⁸ Ω·m, while glass has ρ ≈ 10¹⁰–10¹⁴ Ω·m — a 22-order-of-magnitude range. Temperature also affects resistance: metals increase resistance with temperature (positive temperature coefficient), while semiconductors decrease (negative coefficient). This is why resistance values span from milliohms to gigohms in practice.
Standard 4-band resistors: the first two bands give digits, the third band is the multiplier (number of zeros), and the fourth band is tolerance. For example, brown-black-orange-gold = 10 × 10³ = 10 kΩ ± 5%. For 5-band precision resistors, three bands give digits, the fourth is the multiplier, and the fifth is tolerance. This calculator helps verify: if you read 4.7 kΩ from color codes, you can confirm it equals 4700 Ω.
At milliohm levels, lead resistance, contact resistance, and thermoelectric voltages all become significant compared to the measurement. A standard multimeter's test leads have 100–500 mΩ resistance, which would dominate a 10 mΩ measurement. The solution is four-wire (Kelvin) sensing: two wires carry the test current, and two separate wires measure the voltage drop directly across the resistor, eliminating lead resistance errors.
Insulation resistance testing (megging) applies a high DC voltage (typically 500–5000 V) across insulation and measures the resulting leakage current to calculate resistance. Good insulation shows GΩ-range resistance. The minimum acceptable value is often 1 MΩ per kV of operating voltage. Values below this threshold indicate moisture ingress, contamination, or insulation degradation. Regular megger testing prevents electrical failures in motors, cables, and switchgear.
Resistance (R) opposes DC current and dissipates energy as heat. Impedance (Z) is the AC generalization that includes resistance plus reactance from capacitors and inductors: Z = R + jX, where X is reactance. Impedance magnitude |Z| = √(R² + X²) is measured in ohms but varies with frequency. At DC (0 Hz), impedance equals resistance. The same unit conversion (Ω, kΩ, MΩ) applies to both resistance and impedance magnitude.
For metals, resistance increases approximately linearly with temperature: R(T) = R₀[1 + α(T − T₀)], where α is the temperature coefficient. Copper has α ≈ 0.00393/°C, meaning a 10% resistance increase for a 25°C rise. This matters for precision circuits and power systems. Semiconductors have negative temperature coefficients — resistance decreases with temperature. Thermistors exploit this effect for temperature sensing. Superconductors have zero resistance below their critical temperature.
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