AWG vs. mm²: Cable for 5A–30A Magnetic Connectors

Quick answer: AWG (American Wire Gauge) is a numbered scale where a bigger number means a thinner wire. mm² is the actual cross-sectional area of the copper, so a bigger number means a thicker wire. For 5A–30A magnetic connectors, size the cable by the current and the heat you can accept, then check voltage drop. Convert units only after that.

If you are buying magnetic connectors from a supplier in China while your cable vendor works in AWG and your drawings say mm², you have probably seen this mismatch. It is a small detail that quietly ruins samples. A connector rated for 12 V and 5 A can look fine on paper and still run warm in your product because the wire attached to it was one size too small.

This guide shows how the two systems relate, how to pick a cable for the 5A to 30A range, and what to tell us when you request a quote. It supports our page on waterproof pogo pin and magnetic connectors for 5A to 30A designs, so you can read both together.

AWG vs. mm²: What Each One Actually Measures

AWG is a North American scale. The numbers run backwards, which confuses everyone at first. A 10 AWG wire is thick, a 24 AWG wire is thin. Each step up in AWG number shrinks the copper area by roughly 21%. Every 3 steps cuts the area in half, and every 6 steps halves the diameter.

mm² is the metric approach used across Europe and most of Asia. It states the cross-sectional area of the conductor directly. A 2.5 mm² wire has 2.5 square millimetres of copper, and the standard sizes follow a preferred series such as 0.5, 0.75, 1.0, 1.5, 2.5, 4, 6 and 10 mm². The IEC 60228 standard defines these nominal conductor sizes for insulated cables, and you can find it in the IEC webstore.

Here is the practical difference. AWG is a gauge number that maps to a specific diameter, so it describes one wire size at a time. mm² is a plain area, so you can use it for any stranded or solid conductor. Neither one tells you the current rating. Current depends on temperature, insulation, bundling, and how long the cable is. That is why cable size and connector rating have to be chosen together.

AWG to mm² Conversion Table

Use this table for the sizes that come up most often with 5A to 30A connectors. The areas are standard values for copper wire, and the resistance figures are for copper at 20 °C.

One rule saves most trouble: when the closest metric size is smaller than the AWG wire (20 AWG becoming 0.5 mm², or 18 AWG becoming 0.75 mm²), step up to the next metric size for the same current. Never round down on a power line.

Why Cable Size Matters for a Magnetic Connector

A connector does not fail because of its label. It fails because it gets too hot. Heat follows P = I² × R, so doubling the current quadruples the heat. We explain this in more depth in the article on why four 5A pogo pins don’t make a 20A connection.

The cable is part of that heat story. A thin wire adds resistance, and resistance creates two problems: voltage drop and heat. Voltage drop matters most on low-voltage products. At 12 V, losing 0.3 V in the cable means your device sees about 11.7 V when it is working hardest, and that is before the connector takes its share.

Here is a comparison worth keeping in mind. The CFE MXA-0010 magnetic connector is rated 12 V, 5 A, with contact resistance listed at 50 mΩ maximum. At that worst-case value, the contact pair dissipates about 1.25 W. A 1 m run of 20 AWG wire out and back carries 5A with a loss of about 1.7 W. The watts are similar, but the heat is not. The cable spreads its loss over two metres. The contact concentrates its loss in a space the size of a fingernail. That is why a slightly undersized wire near a connector can push the whole assembly hot.

What the numbers look like in practice

This table shows loss for a 1 m cable (2 m of copper, out and back) at the starting sizes we describe below. It uses copper at 20 °C and a 12 V supply. Warm copper has higher resistance, roughly 20% to 25% higher at 80 °C, so treat these as best-case figures.

Notice that the heat grows even though the voltage drop looks calm. At 30A, nearly 6 W is still heating the wire and the insulation around it. That is real, and it is the reason the rating of the cable insulation matters as much as the gauge.

Picking a Cable for 5A, 10A, 20A, and 30A

There is no single correct gauge for a given current, because the answer depends on length, temperature rise, and insulation. What helps is a starting point you can test against your own product. The sizes below are conservative starting points for short runs, around one metre, at low voltage. They are not a substitute for a temperature test on your finished assembly.

Four questions move you inside each range:

• How long is the run? Resistance scales with length. A 3 m cable has three times the loss of a 1 m cable at the same gauge.
• Is the load continuous? A battery charger that holds 20A for hours heats a cable far more than a tool that draws 20A for ten seconds.
• Where does the cable run? A wire inside a sealed enclosure, wrapped with other wires, sheds heat badly.
• What is the supply voltage? A 0.3 V loss is minor at 24 V and painful at 5 V.

For a 30A design, the cable is rarely the only limit. The PCB copper and the pin series matter just as much, and our guide to reading a pogo pin connector datasheet shows which specifications to check first.

Stranding, Insulation, and Fit: Where Gauge Alone Misleads

Two cables with the same AWG can behave very differently. Three details are worth checking before you order.

Stranded or solid

Magnetic connectors exist to be connected and disconnected, and the cable behind them usually flexes. Stranded copper tolerates bending far better than solid wire, which work-hardens and cracks. IEC 60228 groups flexible conductors into their own classes for this reason. For any moving or frequently handled cable, specify stranded and ask for the strand count.

Insulation

Insulation sets the temperature ceiling and the outer diameter. A thin-wall insulation lets you fit a larger copper area into a tight space, but it may not tolerate the heat of a 20A load. A thick jacket gives better abrasion resistance but adds bulk. Tell your cable supplier the maximum operating temperature, not just the gauge.

Termination fit

A larger wire has to physically fit the connector’s solder cup, solder tail, or crimp. This is where a design on paper meets reality. A 10 AWG wire does not fit a terminal designed for 18 AWG, and forcing it by trimming strands throws away the copper area you paid for. Confirm the terminal bore or tail size against the wire’s strand diameter before you finalise the harness.

Matching Cable to CFE Magnetic Connectors and Pogo Pins

CFE’s 5–30A magnetic connector category currently lists the MXA-0010 2-pin magnetic DC power connector, rated 12 V, 5 A, with a magnetic force of 4.6 N and a 20,000-cycle life test. For this part, a 20 to 18 AWG cable is a sensible starting point, assuming a short run.

Its datasheet lists a contact resistance of 50 mΩ maximum for both the male and female parts. The female side is listed at 12 V, 1 A, which is a reminder to read the ratings for each half of a mated pair, not just the headline figure.

For higher currents, look at the 5A–30A high-current pogo pin range. The BP38111 is listed at DC 12 V, 30A, with a 20,000-cycle life test. Plating is gold, adjustable to customer requirements. At this level the cable, the solder joint, and the board copper all carry real heat.

If your product needs a different current, pin count, or cable gauge than the standard parts, the team can build around it. See custom pogo pin connectors and magnetic cables for what is available.

Common Mistakes When Sizing Cable for Magnetic Connectors

• Converting by eye. Reading “18 AWG” as “about 1 mm²” overstates the copper by roughly 20%. Use the table.
• Sizing for the connector’s headline rating only. The connector’s current figure assumes the rest of the circuit keeps up.
• Ignoring the return path. A 1 m cable has 2 m of copper in the loop, which doubles the loss.
• Splitting current across thin wires. Four small wires on four small pins rarely share current evenly. This is the same trap covered in our 20A pogo pin article.
• Skipping the temperature test. Tables get you to a good first sample. Only a loaded assembly tells you the truth, which is also why we suggest reading why pogo pins fail early in the design.
• Forgetting moisture. In wet environments, powered contacts corrode quickly, which raises resistance and heat. See why powered pogo pin contacts corrode in water.

What to Send With Your Quote Request

A short, complete brief gets you a correct recommendation on the first reply. Include:

• Operating current and peak current, plus voltage
• Cable length in metres, and whether it is bundled or enclosed
• Duty cycle and the temperature rise you can accept
• The cable you plan to use, in AWG or mm², with strand count and insulation rating
• Water exposure, if any
• Space limits, pitch, and mounting style
• Expected mating cycles and order quantity

Send those details through our quote and samples page, or email cfe@cfeconn.com. If you are still choosing between connector families, start with the 5A–30A waterproof pogo pin and magnetic connector guide.

Frequently Asked Questions

What is the difference between AWG and mm²?

AWG is a numbered gauge where a higher number means a thinner wire. mm² is the actual copper cross-section area, where a higher number means a thicker wire. Neither one gives a current rating by itself.

What AWG is 1 mm²?

1 mm² falls between 18 AWG (0.823 mm²) and 16 AWG (1.31 mm²). For a power connection, use the thicker of the two options if you are unsure.

What wire gauge do I need for a 30A magnetic connector?

A common starting point for a short run is 10 to 8 AWG (about 6 to 10 mm²). The right size depends on cable length, duty cycle, insulation, and ambient temperature, so confirm it with a temperature test on your assembly.

Does a thicker cable make a connector safe for higher current?

No. The connector’s contact resistance, pin rating, and the PCB copper also limit current. A thicker cable removes one weak point but not the others.

Can I use the same cable for 5A and 10A connectors?

You can use one cable at both currents only if it is sized for the higher one. A cable chosen for 5A will heat and drop voltage at 10A.