Megaohms to Milliohms Converter

How to Convert Megaohms to Milliohms

To convert an electrical resistance measurement from megaohms to milliohms, multiply the resistance value by the conversion factor. Since one megaohm is equal to 10⁹ milliohms, you can use this formula:

The resistance in milliohms is equal to the megaohms multiplied by 10⁹.

How Many Milliohms Are in a Megaohm?

There are 10⁹ milliohms in one megaohm.

What Is a Megaohm?

The megaohm (symbol: MΩ) is a unit of electrical resistance equal to one million (10⁶) ohms. The prefix “mega” denotes a factor of 10⁶ in the International System of Units. Megaohms are used to express high resistances found in insulation testing, sensor circuits, and precision measurement. Insulation resistance testing (commonly called “megger testing”) measures the resistance of electrical insulation in cables, motors, and transformers, with acceptable values typically in the megaohm range. In cable insulation testing, new cables should have insulation resistance of at least 1–5 MΩ per 1,000 feet. Motor winding insulation should typically test at 1–2 MΩ or higher. Values below 1 MΩ often indicate moisture ingress or insulation degradation. In high-impedance circuits, such as pH meters, electrometers, and ionisation chambers, input impedances of 10–10,000 MΩ are common. These instruments require special guarding techniques to prevent leakage currents from affecting measurements. The input impedance of an oscilloscope probe is typically 10 MΩ, and the input impedance of a standard digital multimeter is usually 10 MΩ as well. These high impedances minimise the loading effect on the circuit being measured.

One megaohm is equal to:

• 10⁶ ohms (Ω)
• 1,000 kiloohms (kΩ)
• 0.001 gigaohms (GΩ)
• 10⁹ milliohms (mΩ)
• 10¹⁵ abohms (abΩ)
• 1.1127 × 10⁻⁶ 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.

Megaohms to Milliohms Conversion Table

The following table shows conversions from megaohms to milliohms.

Related Resistance Converters

Convert from Megaohms

Convert to Milliohms