What Does "100–240V" Mean? (Dual Voltage Explained)

Most modern chargers — phones, laptops, cameras, tablets, most CPAP machines — are dual voltage. The label reads something like "INPUT 100–240V~ 50/60Hz".

You'll find the rating on the device, its plug, or its power brick. The voltage range is the part that matters for safety.

If the label shows only a single value such as "120V" or "220–240V", the device is single voltage and is not safe to plug into a different voltage without a converter.

Do not confuse input with output. A USB-C charger may say "65W" or "20V output"; the travel-safety line is still the AC INPUT rating, usually printed near the pins or on the power brick.

Label examples

Dual-voltage labels that are safe to recognize

Look for the AC input range, not the USB output or brand name.

INPUT 100-240V~ This is the travel-safe voltage range for most chargers and power bricks.

50/60Hz For switch-mode chargers, this usually means the same brick works on both common grid frequencies.

OUTPUT 20V 3.25A This is low-voltage DC output to your device. It does not replace the AC input check.

Visual proof

Label examples to recognize

Use these text patterns as visual cues before you trust a charger, hair tool, or adapter abroad.

Travel-safe AC input INPUT 100-240V~ 50/60Hz This is the wall-side range that usually works worldwide; you may still need a plug adapter.

Single-voltage warning INPUT 120V~ 60Hz This is not universal. Do not rely on a plug adapter in 220-240V countries.

Output is not input OUTPUT 20V ⎓ 3.25A USB-C output tells you what the charger sends to the device; it does not prove wall-voltage safety.

Related guides

Guidance only — not professional electrical advice. Always confirm against your device's label before plugging in. Local wiring (especially in hotels and older buildings) can vary.