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.
The two global standards — and why they exist
The 120V / 60 Hz standard originated in North America through early electrification by Edison and Westinghouse. The higher 220–240V / 50 Hz standard was adopted across most of Europe and its colonies, partly because higher voltage allows thinner (cheaper) wiring over longer distribution runs. The result is a world split into two largely incompatible zones.
Japan is the most unusual case: the western half (Osaka, Kyoto, Hiroshima) runs at 60 Hz while the eastern half (Tokyo, Sapporo) runs at 50 Hz, both at 100V, because early electrification used German equipment in the east and American equipment in the west.
How to read device labels
The rating plate is always the authoritative source. Common label patterns:
| Label | Means | What you need |
|---|---|---|
100-240V, 50-60 Hz | Dual-voltage, universal | Plug adapter only |
120V, 60 Hz | Single-voltage US spec | Step-up converter at 230V destinations |
230V, 50 Hz | Single-voltage EU spec | Step-down converter at 120V destinations |
100V, 50/60 Hz | Single-voltage Japan spec | Converter at most other destinations |
A converter must be rated to handle more watts than the device draws — if it is listed in VA rather than watts, multiply by 0.8 to get a conservative watt equivalent.
Frequency matters more than you might expect
For modern electronics — phones, laptops, LED drivers — frequency makes essentially no difference because their switch-mode power supplies handle any input. But frequency matters a great deal for:
- Synchronous motors in clocks, fans, record turntables, and some washing machines. A 60 Hz appliance runs 20% fast on a 50 Hz grid and vice versa.
- Transformer-coupled audio equipment that is tuned to 50 Hz may hum noticeably on a 60 Hz supply, or the transformer may run warmer.
- Some older heating elements regulated by a frequency-locked timer.
When in doubt, check whether the device has a motor or a timing circuit before assuming that a dual-voltage label is all you need.
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.
- Never rely on visual inspection of the socket. Some countries use European sockets but run 127V rather than 230V — the database is more reliable than the physical hardware.