How to Convert Ohms to Milliohms
To convert an electrical resistance measurement from ohms to milliohms, multiply the resistance value by the conversion factor. Since one ohm is equal to 1,000 milliohms, you can use this formula:
The resistance in milliohms is equal to the ohms multiplied by 1,000.
Using the formula: milliohms = ohms × 1,000
milliohms = 5 Ω × 1,000 = 5,000 mΩ
Therefore, 5 ohms equals 5,000 milliohms.
How Many Milliohms Are in a Ohm?
There are 1,000 milliohms in one ohm.
What Is a Ohm?
The ohm (symbol: Ω) is the SI derived unit of electrical resistance, named after German physicist Georg Simon Ohm. It is defined as the resistance between two points of a conductor when a constant potential difference of one volt applied across these points produces a current of one ampere (1 Ω = 1 V/A). The ohm is the fundamental unit for expressing electrical resistance in science and engineering worldwide. It is central to Ohm’s Law (V = IR), which relates voltage, current, and resistance in electrical circuits. In everyday electronics, resistor values span from fractions of an ohm to millions of ohms. A typical LED current-limiting resistor might be 220–470 Ω, a pull-up resistor 4,700–10,000 Ω, and the impedance of headphones 16–600 Ω. The ohm is also used to express impedance (the AC equivalent of resistance) in audio, radio frequency, and telecommunications engineering. Standard impedances include 50 Ω (RF equipment), 75 Ω (coaxial cable, video), and 8 Ω (loudspeakers). In the modern SI, the ohm is realised through the quantum Hall effect, which provides an extremely precise resistance standard. The von Klitzing constant RK = h/e² ≈ 25,812.807 Ω is used as the primary standard for resistance calibration.
One ohm is equal to:
- 1,000 milliohms (mΩ)
- 106 microohms (μΩ)
- 109 nanoohms (nΩ)
- 0.001 kiloohms (kΩ)
- 109 abohms (abΩ)
- 1.1127 × 10−12 statohms (statΩ)
What Is a Milliohm?
The milliohm (symbol: mΩ) is a unit of electrical resistance equal to one thousandth (10−3) of an ohm. The prefix “milli” denotes a factor of 10−3 in the International System of Units. Milliohms are used in power electronics, battery testing, and current sensing applications. The internal resistance of batteries is typically measured in milliohms — a fresh alkaline AA battery has an internal resistance of about 100–300 mΩ, while a lithium-ion cell might have 20–80 mΩ. Higher internal resistance indicates ageing or degradation. In current sensing, low-value resistors (called shunt resistors or sense resistors) in the milliohm range are placed in series with a circuit to measure current by sensing the voltage drop. Common values include 1 mΩ, 5 mΩ, 10 mΩ, and 100 mΩ. In PCB (printed circuit board) design, the resistance of copper traces carrying high currents is in the milliohm range. A 1-ounce copper trace that is 1 inch wide and 10 inches long has a resistance of approximately 5 mΩ. The resistance of fuses, circuit breaker contacts, and motor windings are also commonly measured in milliohms for quality assurance and predictive maintenance.
One milliohm is equal to:
- 0.001 ohms (Ω)
- 1,000 microohms (μΩ)
- 106 nanoohms (nΩ)
- 106 abohms (abΩ)
- 1.1127 × 10−15 statohms (statΩ)
Understanding Electrical Resistance Units
Electrical resistance is a measure of the opposition to the flow of electric current through a conductor. It is defined by Ohm’s law as the ratio of voltage to current (R = V/I). Resistance depends on the material’s resistivity, the length of the conductor, and its cross-sectional area (R = ρL/A).
Resistance converts electrical energy into heat, which is the basis of resistive heating in toasters, electric heaters, and incandescent light bulbs. In electronic circuits, resistors are used to control current flow, divide voltages, bias active components, and set time constants.
Major Resistance Unit Families
- SI units: The ohm (Ω) is the SI unit of resistance, with standard metric prefixes: nanoohm (nΩ = 10−9 Ω), microohm (μΩ = 10−6 Ω), milliohm (mΩ = 10−3 Ω), kiloohm (kΩ = 103 Ω), megaohm (MΩ = 106 Ω), and gigaohm (GΩ = 109 Ω).
- CGS-EMU unit: The abohm (abΩ) is the resistance unit in the electromagnetic CGS system. 1 abΩ = 10−9 Ω = 1 nΩ.
- CGS-ESU unit: The statohm (statΩ) is the resistance unit in the electrostatic CGS system. 1 statΩ ≈ 8.988 × 1011 Ω, an extremely large value reflecting the different scaling of ESU electrical quantities.
Resistance in Everyday Life
- Wiring: Household copper wiring has very low resistance (milliohms per metre) to minimise voltage drops and heating.
- Electronics: Resistors in circuits range from fractions of an ohm (current sense) to megaohms (high-impedance inputs).
- Insulation: Good electrical insulation has resistance in the megaohm to gigaohm range, preventing current leakage.
- Human body: Dry skin has a resistance of 10,000–100,000 Ω, but wet skin can be as low as 1,000 Ω, which is why water and electricity are dangerous together.
Converting Between Resistance Units
All resistance units measure the same physical quantity, so converting between them requires multiplying by the appropriate conversion factor. For SI prefixed units, each step is a factor of 1,000. The CGS units involve the speed of light constant for the statohm, while the abohm is simply 10−9 ohms.
Tips for Resistance Conversions
- For SI prefix conversions (nΩ, μΩ, mΩ, Ω, kΩ, MΩ, GΩ), each step is a factor of 1,000. So 1 kΩ = 1,000 Ω = 1,000,000 mΩ.
- The abohm is exactly equal to the nanoohm: 1 abΩ = 1 nΩ = 10−9 Ω. They’re interchangeable.
- The statohm is an enormous unit: 1 statΩ ≈ 899 GΩ. It is rarely used in modern practice.
- To convert ohms to kiloohms, divide by 1,000. To convert kiloohms to megaohms, divide by 1,000 again.
- Resistor colour codes and standard values (E-series) are always expressed in ohms. A “4.7k” resistor is 4,700 Ω = 4.7 kΩ.
- In schematics, resistance values are often shortened: 4k7 = 4.7 kΩ, 2M2 = 2.2 MΩ, 47R = 47 Ω.
- The relationship between statohm and abohm involves the speed of light squared: 1 statΩ = c² × 1 abΩ (in CGS units), or about 8.988 × 1020 abohms.
- When measuring very low resistances (milliohms and below), always use four-terminal (Kelvin) connections to eliminate lead resistance errors.
Ohms to Milliohms Conversion Table
The following table shows conversions from ohms to milliohms.
| Ohms | Milliohms (mΩ) |
|---|---|
| 1 Ω | 1,000 |
| 2 Ω | 2,000 |
| 3 Ω | 3,000 |
| 4 Ω | 4,000 |
| 5 Ω | 5,000 |
| 6 Ω | 6,000 |
| 7 Ω | 7,000 |
| 8 Ω | 8,000 |
| 9 Ω | 9,000 |
| 10 Ω | 10,000 |
| 11 Ω | 11,000 |
| 12 Ω | 12,000 |
| 13 Ω | 13,000 |
| 14 Ω | 14,000 |
| 15 Ω | 15,000 |
| 16 Ω | 16,000 |
| 17 Ω | 17,000 |
| 18 Ω | 18,000 |
| 19 Ω | 19,000 |
| 20 Ω | 20,000 |
| 21 Ω | 21,000 |
| 22 Ω | 22,000 |
| 23 Ω | 23,000 |
| 24 Ω | 24,000 |
| 25 Ω | 25,000 |
| 26 Ω | 26,000 |
| 27 Ω | 27,000 |
| 28 Ω | 28,000 |
| 29 Ω | 29,000 |
| 30 Ω | 30,000 |
| 31 Ω | 31,000 |
| 32 Ω | 32,000 |
| 33 Ω | 33,000 |
| 34 Ω | 34,000 |
| 35 Ω | 35,000 |
| 36 Ω | 36,000 |
| 37 Ω | 37,000 |
| 38 Ω | 38,000 |
| 39 Ω | 39,000 |
| 40 Ω | 40,000 |