Is 10GB enough for a week in Japan?

For most travellers, yes, and often for two weeks. If the heavy evening use runs on hotel or cafe Wi-Fi, where you find it, the eSIM only carries maps, train times, translation and messaging. Daily streaming or video calls on mobile data are what push people to 20GB.

Is 20GB enough for a month in Japan?

For a normal month it usually does, especially if you have Wi-Fi where you sleep. If you work remotely with daily video calls, watch your usage in the first week: a top-up or the 50GB plan gives you room without the stress.

How much data does a maps app use in Japan?

Very little, roughly 5 to 20 MB an hour, so a week of navigating stations and streets barely registers. Translation with the camera and video autoplay in social feeds use far more.

Do I need data on the shinkansen?

You will want it for seat and platform information and for the hours in between: Tokyo to Kyoto is around two and a half hours, which is a lot of scrolling if you fill it that way. Downloading what you want to watch before you board is the cheapest option.

Can I rely on Wi-Fi in Japan instead?

Not on its own. Wi-Fi, where you find it, can stretch any plan, but it stops at the door: it covers where you are sitting, not the platform where you need the next train or the street where you need the right exit, and public networks are the wrong place for banking.

What happens if I run out of data in Japan?

You buy a top-up rather than starting over, so running low is an inconvenience, not a trip-ender. Check your usage in your phone settings after the first couple of days and top up only if the trend says you need it.

How much data do you need in Japan?

The short answer

For a typical trip to Japan, 10GB comfortably covers one to two weeks. If you work remotely, stream, or stay longer, 20GB is the safer pick, and 50GB is for hotspotting a laptop or sharing across a trip. The answer is a range rather than a number because of Wi-Fi: hotel or cafe Wi-Fi, where you find it, can take some of the load, but it stops at the door, so your eSIM carries you on platforms, in taxis and between towns. The more of your heavy use runs on Wi-Fi, where you have it, the further any plan stretches.

What actually uses your data

Most people overestimate the light things and underestimate the heavy ones. Rough hourly figures, which shift with quality settings and signal:

Maps and navigation: about 5 to 20 MB an hour. A whole week of station-to-station navigating barely dents a plan.
Messaging and voice calls: under 30 MB an hour. Texts, voice notes and voice calls cost almost nothing in data terms.
Social scrolling: roughly 500 MB to 1 GB an hour. Instagram and TikTok are the quiet budget-eaters, because autoplay video adds up fast.
Video calls: about 200 to 700 MB an hour. A daily call home or a work stand-up is the line that pushes remote workers from 10GB toward 20GB.
Streaming video: 1 to 3 GB an hour. HD video is by far the heaviest thing a phone does, and it is what fills a 50GB plan.

A realistic day in Tokyo

Picture an ordinary day: the map open to find the right exit out of a station that has dozens, train times checked twice, the camera translating a menu because menus are often not bilingual even where signage is, a few photos sent home from the Shibuya scramble, an hour of scrolling on the train, a short video call, messages throughout. Off Wi-Fi, that comes to roughly 1 to 1.5 GB. Put a couple of evening episodes on mobile data instead of Wi-Fi and you can double it. A light to moderate week lands around 5 to 8 GB, and a heavier or longer trip climbs from there.

What nudges Japan travellers up or down

A few things specific to Japan tip the balance. Translation is constant: station names are romanised and major signage is bilingual, but menus, ingredient labels and vending machines often are not, so the camera works all day. Rail is app-shaped: timetables, platform numbers and IC card balances live on your phone, and the map is open between them. Long shinkansen legs are quiet hours where scrolling or a downloaded film replaces the view. Pulling the other way, hotel or cafe Wi-Fi, where you find it, can take the heavy use off your plan: if your evening streaming runs on Wi-Fi rather than mobile data, a 10GB plan can last a fortnight.

Matching it to a plan

The three plans map onto this simply. 10GB suits a normal one to two week trip. 20GB is the comfortable choice for remote work, heavier social and streaming, or a longer stay. 50GB is for hotspotting a laptop, streaming freely, or sharing across a trip. All three run for 30 days, and if you misjudge it you can buy a top-up instead of starting over, so it is safe to pick the smaller plan when unsure. Goodbars sells a Japan eSIM you install at home and switch on when you land; it runs on NTT docomo, Japan's largest mobile network by mobile contracts, and our Japan coverage page shows where it reaches and what independent speed tests measure. See the plans for the detail.

The only way to be certain

Your own habits beat any estimate, including this one. Your phone already tracks mobile data use in its settings, under Cellular on an iPhone and Network or SIM usage on Android. Install the eSIM before you fly, switch it on when you land, and check the number after two days in Tokyo, which is usually the heaviest part of a trip for maps and translation. If you are using less than you feared, relax. If not, you have days of warning and can top up rather than running dry on a platform somewhere in Kansai. It is a far better guide than any table.