What are the two main voltage standards?

The world splits roughly into a 100-127V band (North America, Japan, parts of South America) and a 220-240V band (most of Europe, Africa, Asia, and Oceania). Plugging a 120V-only device into a 230V socket can destroy it, while a 230V device on 120V often simply underperforms or fails to start.

What is the difference between 50 Hz and 60 Hz?

Frequency is how many times per second the alternating current reverses direction. Most of the world uses 50 Hz; the Americas and a few other countries use 60 Hz. Modern electronics with switching power supplies handle either, but clocks, motors, and some older appliances can run slow or fast on the wrong frequency.

Do I need a voltage converter?

Only if your device is single-voltage and the destination differs. Check the label: if it reads 100-240V, it is dual-voltage and needs only a plug adapter. If it reads a single value like 120V, you need a step-up or step-down converter rated above the device's wattage to use it abroad safely.

Why does the UK list 230V when older sources say 240V?

The UK historically ran at 240V and continental Europe at 220V. Both were harmonized to a nominal 230V with a wider tolerance band, so equipment is interchangeable. In practice UK sockets still often measure close to 240V, which is within the 230V tolerance.

Voltage & Frequency by Country

Q: Is the voltage exactly the listed value?

No — these are nominal values. Real grid voltage varies within a tolerance, typically plus or minus 10 percent. A 230V grid may deliver anywhere from about 207V to 253V. Devices are designed to tolerate this range, so the nominal figure is what you use for compatibility checks.

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Mains electricity comes in two broad standards worldwide: a lower 100–127V band and a higher 220–240V band, each running at either 50 Hz or 60 Hz. Using a device on the wrong voltage can destroy it. This reference lists the nominal voltage and frequency for countries worldwide so you can confirm compatibility before you travel.

How it works

Each country is mapped to its nominal mains voltage and frequency. The figures are nominal — real grid voltage varies within roughly ±10%, so a 230V grid may deliver anywhere from about 207V to 253V, all within tolerance.

To decide on a converter, compare the destination voltage with the rating printed on your device. A label reading 100-240V means the device is dual-voltage and works anywhere with just a plug adapter. A single value like 120V means you need a voltage converter (rated above the device’s wattage) at a 220–240V destination, or risk damage.

Tips and examples

100–127V / 60Hz: USA, Canada, Mexico, most of South America.
100V / 50–60Hz: Japan (split-frequency country).
220–240V / 50Hz: most of Europe, Africa, Asia, Oceania.
Dual-voltage devices (100-240V) need only an adapter — check the charger label first.
Nominal values carry a ±10% tolerance; the UK’s 230V often measures near 240V.