eSIM Data Calculator

How much data you need while travelling depends on what you do each day

This eSIM data calculator turns your trip length and a typical day without Wi-Fi (maps, search, social media, short videos, video and calls) into a number of GB. As an example, 2 weeks in Japan with 2 hours of maps, 1 hour of search, 1 hour of social media, 30 minutes each of short videos, video and music, 20 photos sent and two short calls a day comes to about 12.3 GB. With a 20% buffer that is about 14.8 GB, so you would look for a total-data plan of 15 GB or more, or a daily plan of 1.5 GB a day.

Usage per activity comes from figures published by mobile operators and app companies. Sources disagree for the same activity, so the result shows the need calculated from a middle value together with a range built from the low and high published values in the table. If you enter the data, validity and price of an eSIM or roaming plan, the calculator also tells you whether it is enough and what it costs per day.

When it helps to run the numbers

• Choosing between a 5 GB and a 10 GB eSIM: fill in a typical day and you get the need including a buffer, plus the next plan size up.
• Deciding whether a daily plan is enough: compare your daily need with the plan's daily allowance, and see in the share bar which activities use most of it.
• Sharing one plan by hotspot or buying two: set the number of people to 2 and you see how many GB one plan has to cover, so you can compare it with two single plans.
• Comparing an eSIM with your carrier's roaming pack: a roaming pack is also a total-data or daily plan, so you can enter it in the comparison box the same way.

How to use it

1. Choose the trip length, the number of people sharing and the buffer. Count the days you will actually use the eSIM, including travel days if you use data outside.
2. Fill in the daily table with what you use on mobile data, not Wi-Fi. Most rows take hours, photos take a count and calls take minutes. For video, also pick a quality.
3. Read the data you need and the total-data and daily plan sizes in the result. The share bar and the line under it show what uses the most and how to cut it.
4. If you have a plan in mind, enter its type, data, validity and price in the comparison box to see whether it is enough and what it costs per day.

The first screen is filled with the 2 weeks in Japan example. The example buttons switch to 1 week in Europe and a weekend city break. Every change recalculates at once.

What the calculator assumes: data per activity

The source range in the table runs from a low end to a high end, each taken from the two published values named in the last column (video is set separately for each quality). It is not the lowest and highest figure across all sources. The base value is the square root of the two multiplied together (the geometric mean). This calculator uses it so that an activity like maps, where published figures differ by more than 90 times, does not lean to one end.

Other published figures mostly fall inside these ranges. SoftBank lists YouTube at standard quality as 450 MB per hour, Netflix HD as 1,300 MB and music streaming as 87 MB. ahamo gives 300 to 500 MB per hour for standard-quality video, and au lists YouTube at 720p, which it classes as high quality (HD), at 12 MB per minute (720 MB an hour). Netflix says that with the quality setting on High, even standard definition can use up to 1 GB an hour, which is above this calculator's standard-quality range (256 to 900 MB). KT lists a KakaoTalk message as 0.01 MB, which agrees with the other sources that text chat uses almost nothing.

How the calculation works

Calls entered in minutes are divided by 60 to get hours, and photos are multiplied by the data per photo. This calculator counts 1 GB as 1,024 MB. It rounds a total-data plan up to the next whole GB (at least 1 GB) and a daily plan up to the next 0.5 GB (at least 0.5 GB).

Adding a 20% buffer gives 12.29 × 1.2 ≈ 14.75 GB, which the screen rounds up to 14.8 GB, so a total-data plan should be 15 GB or more. The daily need is about 1.1 GB, so a daily plan should give 1.5 GB a day. Video is the biggest item (27%), followed by short videos (20%) and social media (15%).

Results for the three examples

The Japan example includes 30 minutes of video a day, which is why its daily use is higher than the others. The weekend break has no video and only 15 photos, and stays around 0.66 GB a day. The Europe example uses about 0.91 GB a day, so a 1 GB daily plan is just enough.

If you travel inside the EU with a SIM from an EU operator, your home plan may already cover the trip. The Commission's roaming page says data used abroad in the EU is charged the same as at home, subject to any fair-use limit your operator applies. Regulation (EU) 2022/612 sets this up to 30 June 2032, and the Commission notes that it does not cover the United Kingdom, although some operators choose to extend it. A calculator like this one matters most for trips outside the EU, such as Japan.

Total-data, daily and unlimited plans

Even if a daily plan is smaller than your daily need, a total-data plan can still be the better fit when your use is uneven. In the comparison box each plan is marked enough, tight or not enough, and the cheapest of the plans that are enough gets a star.

Ways to use less data

• Offline maps: Google Maps lets you download areas to your phone and navigate offline. Download your destination on hotel Wi-Fi before you go. Google notes that offline maps are not available in some countries or regions.
• Lower the video quality: by this calculator's figures, standard instead of low saves about 251 MB an hour, and standard instead of high saves about 759 MB. In the Netflix app you can choose a data usage setting.
• Low Data Mode and Data Saver: iPhone has Low Data Mode, and Pixel phones have Data Saver, to cut mobile data use.
• Turn off data roaming on your home line: on an iPhone with dual SIM, data roaming is set for each number separately. Switching it off for your home number means data goes only through the travel eSIM.
• Back up photos and update apps on Wi-Fi: this calculator does not count cloud backup or app updates, so set them to Wi-Fi only.

Common mistakes

• Counting Wi-Fi time: video you watch at the hotel does not use eSIM data. Enter only what you use outside, or the need will be inflated.
• Forgetting people on your hotspot: leaving people at 1 when two of you share a plan halves the result.
• Plans that count 1 GB as 1,000 MB: this calculator counts 1 GB as 1,024 MB. If a plan uses 1,000 MB, you get about 2.3% less, so keep a buffer.
• Entering calls as hours: voice and video call rows are in minutes. A 30-minute video call is 30.

Limits

• Published figures are rough values for one app used on its own. Real use depends on app settings, automatic quality changes, ads and network conditions, and activities with widely different sources, such as maps, give a wide range.
• Uploading video, automatic cloud backup, app updates and laptop hotspot work are not counted. If you do these, use a larger buffer.
• The plan comparison uses only the data, validity and price you enter. It does not check a real plan's speed limits, network or hotspot rules.
• The plan sizes (1 GB and 0.5 GB steps) are this tool's own rounding rule. The sizes a seller offers may differ.

As of The sources were checked on 2026-11-08.

Sources

• 01Netflix Help Center: How to control how much data Netflix usesPer device per hour: Low up to 0.3 GB, Medium 0.7 GB, High 3 GB. On mobile, Automatic about 4 hours per GB, Save Data about 6 hours per GB
• 02Vodafone España: Cuántos gigas necesito al mes: ¿Cómo calcularlo? (in Spanish)Table of data per hour by app (Google Maps 550 MB, YouTube 600 to 900 MB, TikTok 300 to 450 MB, WhatsApp video call 300 to 900 MB and more)
• 03ahamo (NTT Docomo): how many GB for overseas travel (in Japanese)Map app about 1 MB per 10 minutes, standard-quality video 300 to 500 MB per hour, 300 MB to 1 GB a day, updated 2026-09-25
• 04SoftBank: data usage guide FAQ (in Japanese)YouTube standard 450 MB per hour, Netflix HD 1,300 MB per hour, music streaming 87 MB per hour, Skype and LINE voice 18 MB per hour, email with photo 3 MB
• 05au: what you can do with 1 GB of data (in Japanese)LINE voice calls about 40 hours and video calls about 3 hours per GB
• 06KT Global Roaming: data use by type of use (in Korean)KakaoTalk message 0.01 MB, live TV standard 5 MB per minute, HD 500 MB per hour
• 07Three UK: How much data do you really need?Music about 500 KB per minute, Facebook post with a photo about 500 KB
• 08Google Maps Help: Download areas & navigate offline in Google MapsSave an area to your phone and use it offline; not available in some countries or regions
• 09Apple Support: Use Low Data Mode on your iPhone and iPadReduces mobile data use
• 10Apple Support: About cellular data roaming options for your iPhone and iPadTurn data roaming on or off, set per number on dual SIM
• 11Pixel Phone Help: Use less mobile data with Data SaverCut mobile data use on a limited plan
• 12EUR-Lex: Regulation (EU) 2022/612 on roaming on public mobile communications networks within the UnionArticle 24: this Regulation expires on 30 June 2032
• 13European Commission: Roaming: connected anywhere in the EU at no extra chargeData used abroad in the EU is charged as at home; fair-use limits; not applied in the UK, though some operators keep it

Frequently asked questions

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