POWER & VOLTAGE
Adapter or converter—which one do you actually need?
The plug decides whether it fits. The voltage decides whether the device survives. Wattage decides whether a transformer is large enough. Order: read the label, check the socket, then consider a transformer only for single-voltage, high-power gear.
Quick answers
What is the difference between an adapter and a converter?
A plug adapter changes pin shape only; voltage stays the same. A transformer changes voltage and must cover the device’s wattage. Dual-voltage (100–240V) chargers usually need an adapter only.
Does a laptop charger need a transformer?
If the label says 100–240V, you usually need only a plug that matches the destination. A transformer is for single-voltage labels, which are rare on laptops.
Japan and the US both take type A. Same voltage?
No. Japan is about 100V, the US about 120V, Taiwan about 110V — the same band, not the same number. Most dual-voltage chargers are fine; single-voltage appliances still follow the label. Japan also splits 50Hz and 60Hz by region.
Must I bring a transformer for a hair dryer?
A heating appliance labelled only 110V or only 220V usually needs a transformer with enough watts in the other band, or you buy/use one locally. Do not force it through a phone-charger adapter.
01Plug, voltage and frequency are three facts#
IEC plug letters (A, B, C, E, F, G, I and others) describe pin shape only. Mains voltage sits in two bands: about 100–127V (Japan, North America, Taiwan and others) and about 220–240V (mainland China, Hong Kong, the UK, most of Europe, Australia). Frequency is 50Hz or 60Hz. Fitting the wall does not mean the voltage matches, and the right voltage does not mean a motor likes that frequency.
Japan also splits 50Hz and 60Hz by region (JNTO explains this). Laptop chargers almost always say 50/60Hz and do not care; motor shavers, some clocks and older appliances might. This site’s plug tool lists typical types and voltages by country; the socket in the room is still the one in front of you.
02Read the volts on the label before you pack a brick#
Phone, laptop and camera chargers usually print 100–240V ~ 50/60Hz. That is dual-voltage: a plug adapter is enough when the wall shape differs; a transformer is not. A device that says only 110V or only 220V is single-voltage. The other band can under-power it or destroy it.
A plug adapter changes shape only. A transformer (sometimes sold as a voltage converter) changes voltage and must cover the device’s watts with margin. Products labelled “travel converter” are often just multi-country plugs. If you cannot tell, pack USB chargers and leave the single-voltage hair dryer at home.
03Typical destinations#
The table is typical household supply, not a promise about every hotel wall. Mainland China is often A/C/I at 220V; Hong Kong is G at 220V; Taiwan is A/B at 110V; Japan is A/B at 100V; the US and Canada are A/B at 120V; the UK and Singapore are G at 230V; much of continental Europe is C/E/F at 230V; Australia is I at 230V. Thailand and others mix several apertures.
Countries mix standards too. Brazil has 127V and 220V cities. Do not order a plug because “Asia is 220V” or “English-speaking means US pins”. Run this site’s lookup for home and destination, then read the charger in your bag.
| Place | Common plugs | Voltage | Dual-voltage USB charger | Single-voltage hair tool |
|---|---|---|---|---|
| Mainland China | A / C / I | 220V | Adapter usually enough | Needs a transformer for 110V units, or leave it |
| Hong Kong | G | 220V | Type-G adapter | Same |
| Taiwan | A / B | 110V | Often fits; US-style pins | Do not plug a 220V unit in |
| Japan | A / B | 100V | Usually fits; frequency splits east/west | Do not plug a 220V dryer in |
| United States / Canada | A / B | 120V | Usually fits | 220V units need a transformer |
| UK / Singapore | G | 230V | Type-G adapter | 100–120V units need a transformer |
| Most of continental Europe | C / E / F | 230V | Euro adapter | 100–120V units need a transformer |
| Australia | I | 230V | Type-I adapter | 100–120V units need a transformer |
04Wattage: a transformer that “fits” can still be too small#
Hair dryers, curling irons and travel kettles are often 1000–2000W. A 50W “voltage converter” is for small electronics; it will overheat on those loads. Dual-voltage USB chargers are tens of watts, not the same class as a heating appliance on the wall.
Buying or borrowing a local-spec dryer at the destination is often lighter than packing a transformer large enough. If the hotel bathroom already has a dryer, leave the 120V one at home. This page does not rate brands; put the W on the device next to the W on the transformer.
05Three trip examples#
Example 1: Tokyo to London. Pins change from A/B to G; voltage from 100V to 230V. A 100–240V laptop charger needs a G adapter only. A 100V-only dryer needs a transformer with enough watts, or it stays home. Example 2: New York to Paris. A/B versus C/E/F, 120V versus 230V. Same split: USB chargers change shape; a US kettle must not go straight into a Euro socket.
Example 3: Shanghai to Taipei. 220V versus 110V; the wall is often mainland type I (angled) against Taiwan A/B (parallel), so you usually still need an adapter — it is not “flat pins look alike, so it will fit”. A dual-voltage charger plus an adapter is usually enough. Do not put a 220V-only appliance on 110V even if its cord is type A; do not put a 110V US mug on a mainland socket. Read the label and the IEC letter, not whether the pins look familiar.
06USB, power strips and “universal” adapters#
One dual-voltage adapter with USB-A/USB-C usually covers phones, earbuds and a laptop. Do not daisy-chain a household power strip onto a travel adapter unless that strip is itself dual-voltage and the plug matches — many strips simply repeat the origin voltage on every outlet.
A “worldwide” adapter still only changes shape. Check that its IEC types include the destination and that it has some overload protection. A cheap adapter that fails is worse than no power. Hotel USB ports are unrated; large devices still use the original charger.
07Common mistakes#
Plugging 110V into 220V; driving a kilowatt dryer from a 50W transformer; treating a travel plug as a voltage converter; assuming flat pins mean the same voltage; ignoring Japan’s frequency split. Taiwan and the US look similar and sit in the same band; Hong Kong is UK G at 220V and does not match mainland sockets.
Another is checking only the destination and not an overnight connection hotel, or using a destination “universal” wall plate to feed a single-voltage appliance the wrong volts. Trust the socket and the label; the IEC table is typical values for planning.
08Checklist before departure#
Photograph or copy V, Hz and W for each device; count how many things charge at once; pack one dual-voltage USB adapter; for heating appliances, confirm transformer watts or leave them. Run this site’s plug lookup for home and destination.
This page follows typical IEC World Plugs values and JNTO’s notes on electricity in Japan. Hotels, rentals and offices mix sockets. The tool’s country row is not a guarantee about one wall.
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MORE GUIDES
Keep reading before you go
Airport security: liquids, electronics and batteries
Most checkpoint queues come from three things: oversize liquid bottles, a laptop buried in the bag, and a power bank in checked luggage. Departure and transfer airports can disagree; pack to the stricter stop.
How big can a carry-on be before it is turned away?
Limits vary by airline, cabin and fare. First check whether the included piece is an under-seat bag or an overhead cabin case, then measure the packed bag with wheels and handles.
What to pack for international travel: a checklist that fits a carry-on
Read the airline’s size and weight first, then pack for the number of days. A bag that fits the sizer empty may not when it is full.