How to Measure Amps With a Multimeter

To measure amps with a multimeter, switch off the circuit, select the correct fused current input and AC/DC mode, then insert the meter in series before restoring power. For learning on a small battery-powered circuit, our pick is the Klein Tools MM420: its Lead-Alert LEDs help with jack placement, and it has mA and µA settings.

Quick picks: choose by the current you need to measure

Compare specifications and all conditions

Learning and small battery circuits

Pick

Klein MM420

Why it fits

Lead-Alert LEDs; mA and µA functions

Work where meter loading matters

Pick

Fluke 87V MAX

Why it fits

Published burden-voltage figures for each current function

Higher current through an accessible conductor

Pick

Klein CL710

Why it fits

AC/DC clamp measurement up to 600 A; no series connection

Full comparison table ↔

Swipe to compare. Row labels stay visible.

Job	Pick	Why it fits
Learning and small battery circuits	Klein MM420	Lead-Alert LEDs; mA and µA functions
Work where meter loading matters	Fluke 87V MAX	Published burden-voltage figures for each current function
Higher current through an accessible conductor	Klein CL710	AC/DC clamp measurement up to 600 A; no series connection

Job	Pick	Why it fits
Learning and small battery circuits	Klein MM420	Lead-Alert LEDs; mA and µA functions
Work where meter loading matters	Fluke 87V MAX	Published burden-voltage figures for each current function
Higher current through an accessible conductor	Klein CL710	AC/DC clamp measurement up to 600 A; no series connection

A series DMM suits a low-voltage circuit whose maximum current you can establish within the meter's limits. If you cannot establish that bound, or need to avoid interrupting the circuit, choose an appropriately rated clamp. For batteries, its jaw must measure DC current; AC voltage capability does not establish that. See the DC clamp meter choices, including guidance for small currents.

• Yes: Series DMM: known low-voltage load within the current input's limits
• Partly: DC clamp: verify DC jaw capability and accuracy at your expected current
• No: Unknown load: do not use a DMM current input to discover its maximum

For appliance energy over time, use our electricity-use logging guide. For voltage, resistance and continuity basics, start with how to use a multimeter.

Best for learning: Klein Tools MM420

The MM420 product page lists Lead-Alert illumination and 10 A AC/DC capability. Its manual gives a 400 mA maximum for the µA/mA input, despite that input's 500 mA fuse. The fuse rating is not permission to measure up to it.

One documentation conflict matters: the specification table lists both 400 µA and 4,000 µA ranges, but the µA operating instructions describe currents below 400 µA. Until Klein clarifies that difference, use the mA function above that threshold. Also, current mode defaults to AC: press SEL and confirm DC on the display for the battery example.

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Best for documented loading: Fluke 87V MAX

The 87V MAX manual lists 0.1 µA resolution on its smallest current range and gives burden-voltage figures, useful when the meter itself changes circuit operation. It still has a routine 10 A current limit; buying this DMM is not our solution for higher-current loads.

Version check: this pick covers the 87V MAX. Fluke also lists 87V MAX CAL, supplied with a traceable calibration certificate with data. Choose that package if your work requires the certificate; check the exact suffix and included accessories on Fluke's model list.

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Higher-current alternative: Klein Tools CL710

The CL710 measures AC/DC current through its jaws up to 600 A. Its manual specifies 10 mA resolution on the 60.00 A range; resolution is not accuracy, so this is not our pick for tiny standby currents.

For current, disconnect its test leads and clamp around a single conductor. Clamping around both outgoing and return conductors can cancel the reading. Select DC when appropriate and follow its zero-offset procedure; this is a different method from putting a DMM in series.

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Buying guide: choose the jack, fuse, range and test duration

The input's current limit, its fuse and its permitted measurement time are different specifications. These figures come from the linked MM420 and 87V MAX manuals, including Fluke's manual supplement.

Fluke additionally specifies above 10 A to 20 A for 30 seconds maximum, followed by 5 minutes off, with accuracy unspecified above 10 A. That is a time-limited allowance, not a continuous 20 A capability. The MM420 manual explicitly says not to exceed 10 A.

Decision: if the maximum is unknown, stop and choose another method. If the known maximum fits the high-current input, begin there when uncertain about the smaller range. Move to mA only after confirming the load, including startup demand, fits that input. Switch circuit power off before changing connections. Auto-ranging adjusts the display range within a function; it does not select a safer jack.

Connect in series: a battery-powered learning circuit

Use a 1.5 V AA alkaline cell in a holder, a 1,000 Ω resistor, connecting wires and insulated clips. This is an illustrative resistor-load circuit, not a vehicle battery or mains exercise. The resistor provides the load; the meter replaces a wire in that load's current path. Never omit the resistor and connect the current input straight across the cell.

The diagram shows the meter replacing one wire. Keep the resistor in the loop throughout:

AA holder (+) -- red [current input -> METER -> COM] black -- resistor --+
AA holder (-) ---------------------------------------------------------+

With the cell removed, inspect the leads, check the current fuse as the manual directs, and connect black to COM. Choose the high-current input/function initially, confirm DC, and attach the clips as shown. Insert the cell to read, remove it before changing the range or jack, and only then select mA for a clearer reading within its limits. For the MM420, that means moving red to the shared VΩ jack and selecting mA/DC.

1. 1

   Power off

   Remove the cell before wiring or changing connections.

2. 2

   Insert the meter

   Bridge a break in the loop; keep the resistor connected.

3. 3

   Read with power on

   Check DC mode, displayed units and the input's time limit.

4. 4

   Power off and restore

   Remove the cell, disconnect the meter and restore the circuit.

After disconnecting, return red to the voltage/Ω input and select a voltage function before putting the meter away. On the MM420, the mA jack is already the voltage jack, but the dial still needs changing. This reduces the chance of making the next voltage measurement through a current path. Fluke's Input Alert warns about a current lead left in place with the wrong function selected; treat any jack warning as a reason to stop and check the setup.

Read amps, milliamps and microamps correctly

Read the unit beside the number, not just the decimal point. A means amperes; mA means milliamperes; µA means microamperes. Divide milliamps by 1,000 to obtain amps; divide microamps by 1,000 to obtain milliamps. NIST's SI prefixes define those factors.

For conversion practice, 6,000 µA = 6 mA, as shown in the 87V MAX manual. A minus sign on a DC current reading indicates reversed polarity relative to the leads. Power off before swapping them. For AC, select A~ rather than DC; True RMS does not remove the meter's range, frequency or time restrictions.

Burden voltage: how the meter changes the circuit

Fluke explains that a current meter drops voltage across itself and can affect circuit operation. The 87V MAX's DC table specifies 1.8 mV/mA on its mA ranges, versus 0.03 V/A on its A ranges.

Calculated example, not a measurement: assume a displayed current of 20 mA. The mA-range burden is 20 × 1.8 = 36 millivolts. That voltage is lost across the meter, leaving less for the load. A circuit that works normally but resets or changes behavior with the meter inserted may therefore be responding to the measurement setup.

Use the published burden for the actual function. A higher-current input can reduce loading but may lose useful resolution; compare both specifications. Do not apply Fluke's figures to the MM420: its cited manual does not publish a burden-voltage table.

Troubleshooting: OL, zero current or a blown fuse

Switch off and disconnect before changing jacks, inspecting wiring or accessing fuses.

Replace a blown fuse with the exact specified type, including voltage and interrupt ratings where stated. Never bridge it or substitute a larger fuse to keep measuring. Fluke provides a fuse-test procedure; use that procedure rather than improvising a powered test.

How we choose

These are research-based recommendations, with no physical product testing. Official product pages, model-specific manuals and Fluke's supplement supply the figures for current inputs, fuses, duration, resolution and loading. The battery circuit is an illustrative setup; the burden example is a calculation, not an instrument reading. Our measurement methodology explains how specifications differ from measured results.

Verdict

Use the MM420 for the low-voltage learning task, respecting its jack limits and µA documentation caveat. Choose the 87V MAX when published loading characteristics matter. For loads outside DMM limits, choose a suitable DC clamp, checking low-current accuracy before assuming a higher maximum means a better tool.