“What size is this wire?” is one of the most common questions in electrical work — and the answer depends on which measurement system you’re reading. Thailand uses square millimeters, while imported equipment often uses AWG. Understanding both, and how to convert between them, is essential for choosing the right wire and avoiding hazards like overheating, voltage drop, and short circuits.
Two Wire-Sizing Systems
- Sq.mm (square millimeter): the Thai standard, measuring the wire’s cross-sectional area. A larger number means a thicker wire with higher current capacity.
- AWG (American Wire Gauge): the US standard, common on imported equipment and machinery. Here a smaller number means a thicker wire — the opposite direction from Sq.mm.
Why a Comparison Chart Matters
A wire-size comparison chart helps electricians and installers convert between the two systems so they can select the correct gauge for the job. Getting this right prevents overheating, voltage drop, and short circuits caused by undersized wire.
Approximate AWG-to-mm² Reference
As a general guide (always confirm against the manufacturer’s data):
| AWG | ≈ mm² |
|---|---|
| 14 | ~2.1 mm² |
| 12 | ~3.3 mm² |
| 10 | ~5.3 mm² |
| 8 | ~8.4 mm² |
| 6 | ~13.3 mm² |
| 4 | ~21.2 mm² |
| 2 | ~33.6 mm² |
How to Choose the Right Wire Size
- Actual current load: calculate amps using watts ÷ volts.
- Safety margin: select wire rated for 20–30% more than the calculated load.
- Installation distance: for runs exceeding 20 meters, increase the wire size by 1–2 levels to offset voltage drop.
- Wire material: copper vs. aluminum, which have different current capacity.
- Environmental factors: temperature, humidity, and installation method all affect performance.
Important Warnings
- Never undersize wire to reduce costs.
- Always consult a professional if you’re uncertain.
- Use only standards-certified wire (Thai TIS or international equivalents).
A wire-size chart should always be combined with technical data and real-world conditions for proper electrical safety.
Get the Right Wire Size from TETA Intertrade
TETA Intertrade is a wire-wholesale specialist stocking TIS-standard copper and aluminum wire across the full range of Sq.mm sizes, with guidance on AWG equivalents for imported equipment. We help you match the correct size to your load, distance, and environment — safely and cost-effectively.
Frequently Asked Questions (FAQs)
Why does a smaller AWG number mean a bigger wire?
AWG is a gauge system based on manufacturing steps, so it runs backwards from area: the more times the wire is drawn down, the higher the AWG number and the thinner the wire. Sq.mm measures area directly, so a bigger number is a bigger wire.
How do I convert AWG to mm²?
Use a comparison chart — for example, AWG 10 is roughly 5.3 mm² and AWG 6 is roughly 13.3 mm². Always confirm the exact value against the manufacturer’s technical data.
Does a long cable run change the size I need?
Yes. For runs over about 20 meters, increase the wire size by 1–2 levels to compensate for voltage drop, so equipment still receives correct voltage.
How much safety margin should I add?
Choose wire rated for about 20–30% more than your calculated current load, so the wire isn’t run at its limit and stays cool and safe.
