Set your multimeter to the ohms setting and touch the two probes to the component you're testing

A multimeter measures electrical properties, and the ohms setting measures resistance — how much a component pushes back against electrical current. To check ohms, turn the dial on your multimeter to the ohms symbol (Ω), touch one probe to each end of the component, and read the number on the display. The component must be disconnected from power and unplugged from any circuit before you test it.

The dial usually has several ohms ranges: 200, 2k, 20k, 200k, and 2M (meaning 200 ohms, 2,000 ohms, 20,000 ohms, 200,000 ohms, and 2 million ohms). Start with the highest range if you don't know what you're measuring. If the display shows 1 or stays blank, switch to a lower range. If the display shows OL (overload), the resistance is higher than that range can measure — switch to a higher range.

Key Takeaways

  • Always disconnect the component from power before measuring ohms, or you risk damaging the multimeter and getting shocked.
  • Start with the highest ohms range on the dial, then move to lower ranges if the display shows 1 or stays blank.
  • A reading of 0 ohms means the component conducts electricity with no resistance; a reading of OL means resistance is too high to measure on that range.
  • Different components have different normal resistance values — a working wire reads near 0, a resistor reads its labeled value, and a broken wire reads OL.

Why you need to disconnect power before testing

Testing resistance while a component is powered or still plugged in will damage your multimeter and can shock you. The ohms setting sends a small current through the component to measure how much it resists. If voltage is already flowing through the circuit, that voltage will flow backward into the multimeter's sensitive circuits and destroy them.

Before you test anything, unplug the device from the wall outlet or remove the battery. If you're testing a component inside a larger device, unplug the whole device first. Wait a few seconds — some devices store charge in capacitors even after unplugging. If you're unsure whether something is powered, test it with the voltage setting first to confirm it's safe.

How to read the display and choose the right range

The multimeter dial has multiple ohms ranges because resistance values vary wildly. A wire might measure 0.1 ohms, a resistor might measure 10,000 ohms, and an open circuit might measure millions of ohms. If you pick a range too low for what you're measuring, the display shows OL (overload). If you pick a range too high, the display shows 1 or a very small number and loses precision.

Start at the highest range (usually 2M for 2 million ohms). Touch the probes to the component. If the display shows a number, you're in the right range — write it down. If the display shows 1 or blank, the resistance is lower than that range measures; turn the dial down one step and try again. If the display shows OL, the resistance is higher; turn the dial up one step. Once you see a stable number between 1 and the range limit, you have your answer.

What different readings actually mean

A reading of 0 ohms (or very close, like 0.1) means the component conducts electricity with almost no resistance — this is what you expect from a wire, a switch in the on position, or a good solder joint. A reading of a few hundred or thousand ohms means the component resists some current but still conducts — this is normal for a resistor (the value should match the colored bands on it) or a heating element.

A reading of OL (overload) or infinity means no current flows through the component at all — this is what you expect from an open circuit, a broken wire, a switch in the off position, or a component that has failed. If you're testing a wire and it reads OL, the wire is broken. If you're testing a resistor and it reads 0, the resistor has shorted out and failed.

Testing common components: wires, resistors, and switches

To test a wire, touch one probe to each end of the wire. A good wire reads 0 or very close to 0 ohms. A broken wire reads OL. If you're testing a long wire and it reads a small number like 5 or 10 ohms, that's normal — longer wires have slightly more resistance than short ones.

To test a resistor, touch one probe to each leg (the metal ends sticking out). The reading should match the value printed on the resistor in colored bands or numbers. A 1k resistor should read around 1,000 ohms. If it reads 0 or OL, the resistor is bad. To test a switch, touch one probe to each terminal. When the switch is on, it should read 0 ohms. When the switch is off, it should read OL. If it reads the same in both positions, the switch is stuck.

Common mistakes that give you wrong readings

Touching the metal probes together while testing gives a false 0 reading — always make sure the probes touch only the component you're measuring. Leaving one probe floating in the air while the other touches the component gives an unstable or OL reading. Hold both probes firmly against the component until the display stops changing.

Testing a component while it's still in a circuit (soldered to a board or plugged into a socket) often gives wrong readings because the rest of the circuit affects the measurement. Desolder or unplug the component first. Testing a component that is still powered is the fastest way to destroy your multimeter — always unplug first. If the display keeps changing or shows different numbers each time, the component may be failing intermittently, or you may not be making solid contact with the probes.

When to use different ohms ranges for precision

The 200 ohms range gives the most precise reading for small resistances like wires and solder joints. The 2k and 20k ranges work well for most resistors you'll encounter in electronics. The 200k and 2M ranges are for very high resistances like insulation, open circuits, or components that are supposed to block current.

If you're testing a resistor labeled 470 ohms, use the 2k range — you'll get a precise reading like 468 or 472. If you use the 200 range, it will show OL because 470 is higher than 200. If you use the 200k range, it will show 0.47 or 0.5, which looks like the resistor is broken when it's actually fine. Matching the range to the expected value gives you a reading you can trust.

Frequently Asked Questions

What does it mean if the multimeter display shows 1?

The display shows 1 when the resistance is lower than the current range can measure precisely. Turn the dial down to the next lower range and test again. Keep going down until you see a stable number between 1 and the range limit.

Can I test resistance while the component is still soldered to a circuit board?

You can try, but the rest of the circuit will affect your reading and you'll get a false result. The best practice is to desolder the component first or test it in isolation. If you must test it in place, note that the reading will be lower than the component's actual resistance.

Why does my reading keep changing when I touch the probes to the component?

You're probably not making solid contact with the probes. Press them firmly against the component and hold them still for a second or two until the display stops changing. If it still bounces around, the component may be failing intermittently or corroded.

What's the difference between testing ohms and testing voltage?

Voltage measures how much electrical pressure is in a circuit — use this when power is on. Ohms measures resistance — use this when power is off. Testing ohms on a powered circuit will destroy your multimeter.

If a resistor reads higher than its labeled value, is it bad?

A reading within 5 to 10 percent of the labeled value is normal — resistors have a tolerance rating printed on them. A reading that's 50 percent higher or more, or a reading of OL, means the resistor has failed and should be replaced.