Guide · updated 10 November 2026
How to Test a Capacitor with a Multimeter
To test a capacitor, switch the equipment off and discharge the capacitor safely through a resistor, take it out of the circuit, then measure it. If your multimeter has a capacitance mode, connect the leads (observing polarity on an electrolytic) and compare the reading with the value printed on the capacitor. Without that mode, use the ohms range: a good capacitor starts at a low reading that climbs steadily towards OL as it charges. A reading that stays at zero means a short, and OL right away on a large capacitor means open.
iPhone and iPad (iOS 17 or later): free on the App Store. Android later.
Safety first
Safety. A capacitor can hold a charge long after the power is off, and some, such as those in power supplies, flash units and motor starters, can hurt you. Switch off and isolate the equipment. Discharge the capacitor through a resistor (for example 1 kΩ to 10 kΩ, rated for the voltage), never by shorting it with a screwdriver, and confirm with the meter on a voltage range that it is at 0 V before you touch it. Never measure resistance or capacitance on a live circuit. Use a meter whose CAT rating and fuse fit the work.
What you need
- A multimeter with capacitance, or at least ohms, such as the OWON OW18B, which has a capacitance range.
- A discharge resistor and insulated leads or clips.
- The capacitor's markings: value in microfarads (µF), voltage rating and polarity.
Steps
- Switch off and isolate the equipment. Wait a moment.
- Discharge the capacitor through the resistor for several seconds. Then check with the meter on volts that it reads about 0 V.
- Remove the capacitor from the circuit, or at least one leg. In the circuit, other parts distort the reading.
- With a capacitance mode: set the dial to capacitance. Press REL with the probes open to zero the stray capacitance of the leads. Connect the leads to the capacitor, red to plus on an electrolytic, and wait for the reading to settle.
- With ohms only: set a high range (for example 1 MΩ or the auto range) and touch the probes to the capacitor. Watch the reading. It should start low and rise toward OL.
- Compare the result with the marking on the capacitor.
What the reading means
Typical values, and meters differ.
| Result | Typical meaning |
|---|---|
| Capacitance within about 10 to 20 % of the marked value | Good; electrolytics are often marked with a tolerance of 20 % or more |
| Capacitance well below the marked value | Dried out or aged: replace it |
| Ohms rises from low to OL | Charging, so the capacitor is probably working. It does not give the value |
| Ohms stays near 0 | Shorted |
| OL straight away on a large capacitor, or 0 µF | Open |
| Resistance that settles at a modest value instead of reaching OL | Leaky |
A multimeter measures capacitance at a low test voltage, so it cannot find every fault. A capacitor that tests fine can still fail under its working voltage or ripple current.
Common mistakes
- Not discharging first. Unsafe, and can damage the meter.
- Testing in the circuit. Parallel components change the result.
- Wrong polarity on an electrolytic, which can damage the capacitor.
Log the result with a Bluetooth meter
A capacitor test is a reading that changes over time, so a Bluetooth meter and the app suit it. The live graph shows the resistance climb or the capacitance settle, instead of you watching the display. One tap saves the settled reading with a note, such as the part's position on the board, and Hold keeps it on screen. If your meter is not one the app reads, type in the value; it is marked as manual. Export as CSV. See live graph and quick capture.
What the app does here, and what it doesn't
| What it does | Plan |
|---|---|
| Type the reading from any instrument; typed values are marked as manual. | Free |
| Swipe the readout to a live graph with min and max lines, pan and zoom. | Free |
| Hold freezes the displayed reading and statistics in the app, independent of the meter's own HOLD. | Free |
| REL shows the difference from a stored reference, for example to null out test-lead resistance. | Free |
| One tap saves the current reading, with an Undo. | Free |
| Export log sessions and test files as CSV, free. | Free |
Not yet, or not planned
- A test file is your record, not a certification.
Questions
How do I discharge a capacitor safely?
Switch the equipment off, then connect a resistor of 1 kΩ to 10 kΩ, rated for the capacitor's voltage, across its terminals for several seconds. Check with the meter on a voltage range that it reads about 0 V.
Can I test a capacitor without a capacitance mode?
Roughly. On a high ohms range a good capacitor shows a reading that rises from low to OL. It shows charging, not capacitance.
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