Electrical Resistance Converter

Electrical resistance is a measure of how much a material opposes the flow of electric current. Every conductor has some resistance, from the tiny milliohm resistance of a copper wire to the megohm resistance of insulating materials. The Ohm (Ω), named after German physicist Georg Ohm, is the SI unit of resistance. Understanding resistance and its unit conversions is fundamental for anyone working with electronics, from hobby projects to professional circuit design. This comprehensive resistance converter helps engineers and technicians quickly convert between all commonly used resistance units.

The Ohm: Foundation of Circuit Analysis

One Ohm is defined as the resistance that allows one Ampere of current to flow when one Volt is applied across it, per Ohm's law: V = IR. Standard resistor values typically range from about 1 Ohm to 10 megohms, with the E12 or E24 series defining preferred values. Carbon film and metal film resistors are available in 1/4W, 1/2W, and higher power ratings. Low-value resistors (under 10 Ω) are often used as current sense resistors, while high values (above 1 MΩ) appear in high-impedance analog circuits and timing applications.

Kilohms: The Common Resistor Range

Most practical resistor values fall in the kilohm (kΩ) range, from 1 kΩ to 999 kΩ. Pull-up and pull-down resistors in digital circuits typically use values around 4.7 kΩ to 10 kΩ. Voltage dividers, operational amplifier feedback networks, and LED current-limiting resistors commonly use kilohm values. The resistance color code on through-hole resistors indicates values; for example, brown-black-red indicates 1 kΩ (10 × 10² = 1,000 Ω). Surface mount resistors use a numeric code where "102" means 10 × 10² = 1,000 Ω = 1 kΩ.

Megohms: High Impedance Applications

Megohm (MΩ) resistors appear in high-impedance circuits, electrostatic discharge protection, and measurement applications. Input impedances of oscilloscope probes are typically 1 MΩ or 10 MΩ. Insulation resistance testing measures values in the megohm to gigohm range. Timing circuits using RC time constants at low frequencies often use megohm resistors paired with capacitors. Static-sensitive circuits may include megohm bleed resistors to safely discharge stored energy while maintaining high impedance during operation.

Milliohms: Low Resistance Measurements

Milliohm (mΩ) measurements are important for power applications, battery contacts, and high-current conductors. Wire resistance, connector contact resistance, and PCB trace resistance are typically measured in milliohms. Current sense resistors for power monitoring often range from 1 mΩ to 100 mΩ to minimize power loss while providing measurable voltage drops. Four-wire (Kelvin) measurement techniques eliminate lead resistance errors when measuring milliohm values, essential for accurate low-resistance testing.

Electrical Resistance Conversion Reference

• 1 Ohm (Ω) = 0.001 kΩ = 0.000001 MΩ = 1,000 mΩ
• 1 Kilohm (kΩ) = 1,000 Ω = 0.001 MΩ = 1,000,000 mΩ
• 1 Megohm (MΩ) = 1,000 kΩ = 1,000,000 Ω
• 1 Milliohm (mΩ) = 0.001 Ω = 10⁻⁶ kΩ
• Ohm's Law: R = V/I (Resistance = Voltage ÷ Current)

Practical Applications

• Circuit Design: Selecting resistors for voltage dividers and current limiting
• Power Calculations: Determining power dissipation in resistors (P = I²R)
• Troubleshooting: Measuring and comparing resistance values in faulty circuits
• Component Selection: Converting between data sheet specifications
• Wire Sizing: Calculating conductor resistance for power distribution
• Quality Control: Testing component tolerance and insulation resistance