How much data should I buy?

Rough per-day figures: maps, chat and email around 300–500MB; add social and photos for roughly 800MB–1.5GB; regular video or video calls 2GB or more. Multiply by your days, then add 20–30% if you will share a hotspot.

This page walks through the arithmetic for landing on a GB figure that actually fits your trip, rather than guessing or padding without a reason. It suits anyone currently choosing a plan and unsure what the number on the page should be, as well as anyone who has run out mid-trip or finished with a large unused balance and wants a sharper estimate next time.

There is no single number that fits everyone, because actual usage depends on your own habits: which apps you open, the video quality you have set, and how many people share the connection from one phone. What works is breaking activity into categories and adding them up, which is more accurate than guessing the whole trip in one go.

Start from what you will actually do

Before looking at figures, picture a typical day of the trip, not your heaviest or lightest, and split activity into groups, because each group consumes very differently. Turn-by-turn navigation running all day uses far more than checking chat periodically, and high-resolution video uses far more than audio-only streaming.

• Maps and navigation: light if used in short bursts, much heavier if left running live all day
• Chat and email: the lightest general category, since it is mostly text and small images
• Social media and browsing photos: moderate to heavy, depending on whether the feed autoplays short videos
• Video streaming and video calls: the heaviest general category, more so at higher resolution settings
• Sharing a hotspot with another device: not an activity itself, but a multiplier on everything above

A rough per-day reference table

The figures below are rough guidance for typical use, not measured or tested from any real network, because data volume always depends on app settings, video resolution and personal habits. Use them as a starting point and adjust to yourself.

Multiplying by days correctly

Once you have picked a daily usage level, multiply by the number of days you will genuinely be online, not the total trip length, because on some days you may sit in accommodation with all-day Wi-Fi or spend hours on a flight using no data at all. Multiplying by every day without thinking usually produces a higher figure than necessary.

1. 1Separate all-Wi-Fi days from days that rely on mobile dataCheck your accommodation and itinerary. On days spent in a hotel or stay with strong all-day Wi-Fi, mobile data use is typically much lower than on days spent out sightseeing.
2. 2Count the actual number of days that depend mainly on mobile dataInclude travel days between cities or countries too, since these are often the days you check maps and travel information more than usual.
3. 3Multiply the daily usage level by the number of days countedUse the figures from the table above as the base and multiply directly to get an initial trip total.
4. 4Add a 20–30% margin if you will share a hotspotIf a travel companion or another device will connect through your hotspot, add the margin to the calculated total, not by multiplying the daily figure again.

A worked example

Say a seven-day trip has three days at accommodation with all-day Wi-Fi and four days spent out sightseeing, using turn-by-turn navigation and posting photos to social media periodically. Those four days sit at moderate to slightly heavy, so at 1GB a day that is 4GB. For the three Wi-Fi days, add a light margin of 200MB each for stepping out to eat or queue, adding roughly 800MB. The total comes to around 4.6GB, rounded up to 5GB for comfort.

What to do if data runs low mid-trip

However carefully you calculate, some trips use more than planned, such as a route that needs longer navigation than expected, or an unplanned long video call. What matters is noticing before data runs out completely, not noticing only once you can no longer connect.

• Check remaining data periodically through an app or the phone's settings, rather than waiting for a system alert
• If the balance is low, cut heavy activity such as video streaming first, keeping what remains for essential maps and messages
• Check your app or plan management page to see whether you can top up or buy a new plan immediately, before data runs out completely

Long trips versus short trips

Short trips are usually easier to calculate because there are fewer days and activity is fairly consistent. Long trips tend to swing between heavier and lighter days more often, so averaging across the whole trip may be less accurate than splitting it into phases, such as a stretch exploring a big city versus several days resting at one base.

How this differs from usage at home

Many people compare data used at home with data used while travelling and find the numbers do not match. Part of the reason is that behaviour itself changes: at home you may be connected to Wi-Fi almost constantly without noticing, whereas while travelling you are often out all day with no Wi-Fi to fall back on, which pushes mobile data use up sharply even if the apps you open look the same.

When an unlimited-style plan makes more sense

Some plans are sold as unlimited data but throttle speed after a threshold, or are unlimited only within a set number of days. If you use data heavily every single day, or your calculation lands near or above the largest fixed-size plan available, this style of plan may be more reassuring, though it is worth reading the throttling terms carefully.

Travelling as a family or group: does the calculation differ?

If travelling as a group where each person carries their own phone with their own plan, calculate each person's habits separately, since someone who posts photos to social media all day will use far more data than someone who only checks chat periodically. Applying one figure to the whole group without separating habits usually leaves some people overbuying and others short.

If one phone will share a hotspot with the rest of the group, go back to the same principle: calculate the phone owner's own total first, then add 20–30% per shared device, rather than multiplying the whole total by the number of people. Hotspot sharing is usually for light tasks like checking maps or messages, not everyone running full heavy use at once.

Why plans are sold in fixed sizes rather than pay-as-you-go

Most travel plans are sold in fixed sizes, such as 1GB, 3GB, 5GB or 10GB, rather than being charged according to actual usage after the trip ends. This means you know the cost for certain before you travel, with no worry about an unexpected charge appearing once you are home, unlike roaming through a home SIM, which sometimes bills by actual usage and can produce surprises.

A side effect of selling in steps is that you will almost never buy an amount that matches your calculation exactly; you always round up or down to a size that actually exists for sale. The general guidance is to round up when your calculated figure sits closer to the next size than the current one, and to accept that a small amount left over at the end of a trip is a normal feature of step-based pricing, not a calculation mistake.

Checklist before you buy

1. Sort the trip's activity into light, moderate or heavy based on real use, not intentions
2. Count the days genuinely depending on mobile data, separate from all-Wi-Fi days
3. Multiply usage level by days, then add a hotspot margin if you will share
4. Round up to a plan size that actually exists for sale, rather than chasing an exact figure
5. When unsure, always pick one size larger than the calculation suggests

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