Travel power guide
What Does "100–240V" Mean? (Dual Voltage Explained)
Direct answer
What Does "100–240V" Mean? (Dual Voltage Explained)
An input rating of 100-240V covers nominal voltages within that range. Confirm the frequency, plug, grounding and exact model instructions separately; the range is not permission to use every outlet.
Updated 2026-10-25
Read your AC INPUT label
Copy the AC INPUT line from your device or power supply. Reading it does not confirm the plug, grounding or manufacturer permission.
100–240V~50/60Hz5V ⎓ 3ARead a label photo (optional)
The photo stays in this browser and is not uploaded or saved by PlugVoltage. Reading starts only when you press the button and downloads several MB. It reads Latin INPUT text; you can always type the line yourself.
Photo reading can confuse digits, INPUT/OUTPUT and punctuation. Compare every value and range with the actual AC INPUT label. Correct mistakes in the text field before reading the values.
- INPUT voltage range
- INPUT frequency
Some values could not be read. Keep them unknown and check the label or manual before use.
How to read the label, word by word
In the illustrative label "INPUT: 100-240V~ 50/60Hz 0.5A", INPUT is the AC supply side, "~" denotes AC, and the voltage and frequency ranges describe the accepted supply. Plug, grounding and the exact manufacturer instructions still require separate checks.
The number after the frequency (for example "0.5A") is how much current the device draws at most. It matters for choosing a power strip or adapter current limit, not for the voltage question.
Labels hide in predictable places: molded into the plastic of a power brick, printed on the face of the plug between the pins, on the underside of an appliance, or inside a battery compartment. If the printing is worn away, check the manual or the manufacturer's specification page for the exact model number.
A range is not the same as two values
A continuous range like "100-240V" means the device adapts to anything in between on its own — nothing to configure. That is true dual voltage.
A pair of discrete values like "115/230V" usually marks a switchable device: somewhere on the housing there is a small selector, often recessed and red. It must be set to match the destination grid before you plug in. On a 230V grid with the switch left at 115V, the device receives roughly double the voltage it expects — the classic burnout.
A single value like "120V" or "230V" is single voltage. Do not plug it into a mismatched supply. A converter is an option only if the exact device, load, frequency and both manufacturers permit it; otherwise leave it at home.
Examples do not verify an entire device category
A phone, laptop or CPAP category is not evidence about your unit. The named Apple and ResMed supplies in the sources are examples, not approval of every charger or medical device.
Frequency: what 50/60Hz does and does not cover
Many dual-voltage electronics also accept both grid frequencies — that is what "50/60Hz" on the actual INPUT label declares. Check the complete label, plug, grounding and manufacturer restrictions before use.
Frequency still matters for devices that use the grid's rhythm directly: simple AC motors can spin faster or slower, and old clock radios or appliance timers that count grid cycles drift on the wrong frequency.
No plug adapter and no ordinary voltage converter changes frequency. If a motorized device is frequency-sensitive, the practical answer is a version built for the destination, not more gear.
No label? Keep compatibility unconfirmed
If the exact input rating or restrictions remain unknown, do not connect the device. A voltage converter is an option only when both manufacturers permit the actual load and use; it does not resolve unknown frequency or grounding.
Before the trip, look up the exact model on the manufacturer's site, or photograph the label of every device you pack — a camera roll of labels answers most airport doubts in seconds.
What the evidence covers
A source supports only the facts, socket types or models listed below. A model example does not verify every device in its category. Confirm your own label and outlet.
- Apple: Important safety information for your Mac · checked: 2026-09-30
Apple lists 100–240V AC, 50–60Hz for the named 70W, 96W and 140W USB-C power adapters. Power adapter specifications. A checked manufacturer family example; not proof for every USB, GaN or laptop charger.
- Kansai Electric: Voltage and frequency in Japan · checked: 2026-09-04
Standard supply is 100V; eastern and western areas use 50Hz and 60Hz respectively. Some appliances use distinct 200V sockets. Voltage and frequency sections and regional map. The utility advises checking the manual or manufacturer. A country average does not establish a specific outlet or appliance rating.
- ResMed: AirSense 11 user guide · checked: 2026-09-30
The AirSense 11 65W supply specifies 100–240V, 50–60Hz; typical and peak consumption differ. Technical specifications, printed page 22 (PDF page 25). Only the named supply and machine are covered. Confirm your own supply, accessories and manufacturer instructions.
Label examples to recognize
Use these text patterns as visual cues before you trust a charger, hair tool, or adapter abroad.
Frequently asked questions
How do I know if my device is dual voltage?
Find the INPUT line on the device, its plug, or its power brick. A range that spans both voltage worlds — "100-240V" — means dual voltage. A single value like "120V" means single voltage.
Is 120V dual voltage?
No. "120V" alone is a single-voltage rating. Dual voltage requires a printed range that covers both the 100-127V and the 220-240V grid families, such as "100-240V".
Are all USB chargers dual voltage?
A phone, laptop or CPAP category is not evidence about your unit. The named Apple and ResMed supplies in the sources are examples, not approval of every charger or medical device.
Does dual voltage mean I can plug in anywhere without an adapter?
Read AC INPUT on the actual device or power supply. A rating such as 100–240V describes voltage; frequency, plug, grounding and manufacturer instructions still need separate checks. USB OUTPUT is not a mains input rating.
What does "INPUT 100-240V~ 50/60Hz" mean exactly?
That input rating covers AC supply from 100 to 240 volts at 50 or 60 hertz. Confirm the full local supply range, actual plug, grounding and manufacturer instructions before using the device.
My label says 110-220V. Is that dual voltage too?
It spans two voltage families, but the exact range still excludes Japan at 100V and a 230-240V grid. The checker returns Check Label outside the printed range. Do not widen a rating based on a voltage family.
Do I need to flip a switch on a 115/230V device?
Yes. Dual-value devices with a voltage selector must be set to the destination voltage before plugging in. A selector left on 115V in a 230V country can destroy the device.
Is dual voltage the same as using a voltage converter?
No. Dual voltage is a property of the device input; a converter changes the supplied voltage. Even a dual-voltage device may need a plug adapter that preserves grounding, and its label and manufacturer restrictions still apply.
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.