What a multimeter tells you about an outlet

A multimeter is a handheld tool that measures electrical voltage, current, and resistance. When you use one on an outlet, it shows you whether power is reaching that outlet and whether the voltage is at the correct level. A working outlet in a US home should read between 110 and 120 volts.

Testing an outlet with a multimeter takes about 30 seconds and tells you whether the outlet itself is the problem when something plugged into it stops working. It does not tell you whether the outlet is safe to use long-term — that requires a dedicated outlet tester or a licensed electrician — but it does tell you whether electricity is flowing to that spot.

Key Takeaways

  • Set your multimeter to AC voltage (marked with a wavy line) before testing any outlet in your home.
  • Insert one probe into the narrow slot and one into the wide slot, or insert both into the two round holes if the outlet is round.
  • A reading between 110 and 120 volts means the outlet is receiving power; a reading of zero means it is not.
  • If an outlet reads zero volts, check whether the circuit breaker for that outlet has tripped, and flip it back on if it has.

Setting up your multimeter

Before you touch the outlet, turn the dial on your multimeter to the AC voltage setting. This is marked with a wavy line (∼) and usually labeled "VAC" or "ACV". Do not use the DC setting, which measures direct current — household outlets use alternating current.

If your multimeter has multiple voltage ranges, select the one marked 200V or higher. This range is safe for household outlets and gives you a clear reading. Some multimeters auto-select the range, so check your manual if you are unsure.

Inserting the probes into the outlet

Hold the multimeter in one hand and look at the outlet. A standard US outlet has two vertical slots — one narrow and one wide — and sometimes a round hole below them. Insert the red probe into the wide slot and the black probe into the narrow slot. Keep your fingers on the plastic parts of the probes, not the metal tips.

If the outlet is a round two-hole design (older homes sometimes have these), insert one probe into each hole. The order does not matter for voltage readings. Push the probes in firmly until they make contact with the metal inside the outlet, but do not force them.

Reading the display

Look at the number on the multimeter screen. A healthy outlet reads between 110 and 120 volts. Anything in that range means the outlet is receiving power correctly. A reading of zero or close to zero means no power is reaching the outlet.

Some multimeters show a negative sign in front of the number if you inserted the probes in reverse order. The negative sign does not mean anything is wrong — it just means you swapped the probes. The voltage is still there.

What to do if the outlet reads zero

If the outlet shows zero volts, the first step is to check the circuit breaker. Go to your electrical panel (usually in a basement, garage, or utility closet) and look for a breaker switch that is in the middle position or flipped toward the "off" side. This breaker controls the outlet you just tested. Flip it all the way to "off" and then back to "on".

After resetting the breaker, test the outlet again with your multimeter. If it now reads 110–120 volts, the breaker had tripped and the problem is solved. If it still reads zero, the circuit may have a deeper problem, and you should contact a licensed electrician.

When to test other outlets on the same circuit

If one outlet is dead but others nearby are working, test a few of the working outlets to confirm they read 110–120 volts. This tells you whether the problem is specific to one outlet or affects the whole circuit. If multiple outlets on the same wall read zero, the breaker for that circuit has likely tripped.

If only one outlet reads zero and the breaker is in the "on" position, that outlet may have a loose connection inside the wall or a failed outlet. Do not use that outlet — contact an electrician to inspect it.

Safety reminders when testing outlets

Never insert anything metal into an outlet except the multimeter probes. Do not touch the metal tips of the probes while they are in the outlet. If you are wet or standing on a wet floor, dry off before testing. Do not test an outlet if you see scorch marks, melting, or burning around it — call an electrician instead.

A multimeter is a safe way to check voltage because it draws almost no current from the outlet. You are not at risk of electrocution from the outlet itself when using one correctly, but always treat outlets with respect.

Frequently Asked Questions

What does it mean if the multimeter reads a very low number like 5 or 10 volts?

A reading below 100 volts usually means the outlet is not receiving full power. This can happen if there is a loose wire in the circuit or a failing breaker. Test another outlet on the same circuit to see if the problem is widespread. If only one outlet reads low, contact an electrician.

Can I test an outlet while something is plugged into it?

Yes. The multimeter probes can fit into the slots even if a device is plugged in. Testing a live outlet (one with something running) gives you the same voltage reading as testing an empty one.

Why does my multimeter show a different number each time I test the same outlet?

Household voltage naturally fluctuates between about 110 and 120 volts throughout the day. Small variations are normal. If the reading jumps wildly or drops below 100 volts, there may be a wiring problem.

Is a multimeter the same as an outlet tester?

No. A multimeter measures voltage. An outlet tester is a small plug-in device that checks whether the outlet is wired correctly and whether it has a proper ground connection. A multimeter tells you if power is there; an outlet tester tells you if the outlet is safe to use.