# How to Choose the Right eSIM Plan Size for Your Vacation > A method for working out how much travel data you actually need, using your own phone's statistics rather than guesswork, and how to pick the validity period. Source: https://viasimo.com/magazine/how-to-choose-esim-plan-size-vacation/ Published: 2026-09-19 Tags: travel-esim, buying-guide, travel-planning --- The most common mistake in buying a travel eSIM is not choosing the wrong provider. It is buying the wrong size, usually too large, as insurance against a scenario that never arrives. Data left over when a plan expires is simply lost, so an oversized plan is a donation. This guide gives you a repeatable method for sizing, based on what your phone already knows about you rather than on generic estimates. In this guide: - [Start with your own numbers](#start-with-your-own-numbers) - [Adjust for how you travel](#adjust-for-how-you-travel) - [Pick the validity, not just the data](#pick-the-validity-not-just-the-data) - [One plan or several](#one-plan-or-several) - [A worked example](#a-worked-example) ## Start with your own numbers Generic estimates are unreliable because usage varies by an order of magnitude between people doing superficially similar things. Your phone has the real answer. **On iPhone:** Settings, then Cellular. Scroll past the toggles to the usage figures. The critical detail is the reset date shown at the bottom, because the running total counts from whenever it was last reset, which for many people is the day they bought the phone. If the period is long, divide accordingly. **On Android:** Settings, then Network and internet, then Data usage. Most manufacturers show a per month figure and a per app breakdown, which is more immediately useful. Take a normal recent month. Then subtract the apps you know run only on home or office wifi, because those will behave differently abroad. What remains is your genuine cellular baseline, expressed per day. That daily figure is the foundation. Everything below adjusts it. ## Adjust for how you travel Three adjustments matter, and they push in opposite directions. **Wifi availability pushes your need down.** Hotels, apartments, cafes and increasingly public transport carry a large share of travel data. If you sleep somewhere with reliable wifi every night, a meaningful fraction of your usage never touches the travel plan at all. Travellers consistently underestimate this, which is a large part of why oversized plans are so common. **Navigation and translation push it up, modestly.** You will use maps far more abroad than at home, and often translation alongside it. Maps are lighter than people assume, in the region of tens of megabytes per hour of active navigation, but the usage is continuous in a way it is not at home. **Video pushes it up enormously.** This is the single variable that decides whether you need 5 GB or 25 GB. Streaming or scrolling short form video on cellular is measured in gigabytes per hour, not megabytes. If you have a habit of watching on the move, size for it honestly rather than resolving to stop. As rough anchors once you have your own baseline: - **Maps, messaging and email only:** 150 to 300 MB per day - **Plus browsing, ride hailing and photo uploads:** 300 to 700 MB per day - **Plus regular social video:** 1 to 2 GB per day, easily more - **Working remotely with video calls and tethering:** 2 GB and up per day ## Pick the validity, not just the data A travel eSIM has two dimensions and buyers routinely consider only one. The [validity period](/glossary/validity-period/) is the window in which the data must be used. When it closes, whatever is left is gone. A 10 GB plan valid for 7 days and a 10 GB plan valid for 30 days are genuinely different products, and the shorter one is cheaper because it is worth less. Two details are worth checking before you buy: **When the clock starts.** Some plans begin counting at installation, others at first connection to a network. That difference can be weeks if you install early, and it is the reason some travellers find a plan expired before their trip began. Install early if you like, but confirm which model your provider uses. **Whether extending is possible.** A [top up](/glossary/top-up/) that adds data is common. A top up that extends validity is less so. If your return flight might move, that distinction matters. Match validity to your trip length plus a small buffer for delays, and no more. ## One plan or several For a single country trip this question does not arise. For a multi country itinerary it usually decides your total cost. A [regional plan](/glossary/regional-esim/) covering a continent or a group of neighbouring countries is normally cheaper than buying each country separately, and it avoids the specific waste of leftover data stranded in three separate pots. On a trip through several European countries, one regional plan is almost always the right answer. Buy single country plans when one destination clearly dominates the trip, when the regional plan excludes somewhere you genuinely need, or when a particular country happens to be unusually cheap on its own. Check the regional plan's country list against your actual itinerary rather than assuming, because regional definitions differ between providers and the edges are where they differ most. ## Four ways people get the size wrong Each of these is common, and each has a specific fix. **Buying for the worst week of your life.** The instinct is to size for a scenario where wifi fails everywhere and you work from a train for a fortnight. That scenario is rare and the insurance is expensive, because the unused portion is not refunded. Size for your realistic trip and keep topping up as the fallback. **Forgetting that hotels have wifi.** A traveller who uses 6 GB a month at home does not suddenly need 6 GB a week abroad, because the evening usage that dominates their home total moves onto hotel wifi. The daytime usage is what the travel plan actually carries. **Sizing for the group.** If you are travelling with family and expect to share your connection, that changes the number substantially, and it is worth being honest about before you buy rather than discovering it on day three. Shared usage is not a rounding error, it is a multiplier. **Ignoring the destination premium.** Data costs differ by market far more than by provider. On an itinerary that includes an expensive country, that leg dominates the bill, so it deserves careful sizing while the cheap legs can be treated generously. ## A worked example A traveller takes a 12 day trip through [Italy](/destinations/italy/) and neighbouring countries. Their phone reports 4.2 GB of cellular use over the last 30 days, of which roughly a quarter is a podcast app they know streams on home wifi. That gives a baseline near 3.2 GB per month, or about 105 MB per day. Abroad, they will navigate constantly, upload photos daily, and watch some video on trains. Call it three times their home rate, so roughly 300 MB per day, or 3.6 GB over 12 days. They will also have hotel wifi every night, which will absorb the heavy evening usage. Against that, they might tether a tablet occasionally. A 5 GB regional plan valid for 15 days fits with headroom, costs less than a 10 GB plan, and leaves room to top up if the trip turns out busier than expected. Buying 20 GB defensively would have cost considerably more and, on these numbers, wasted most of it. That is the whole method: start from your own figure, multiply for travel behaviour, subtract for wifi, add a modest buffer, and buy the validity that matches your dates. If you want to take it further, our guide to [getting the most data for your money](/magazine/most-data-for-the-price-esim-plans/) covers price per gigabyte and why unlimited plans are not what the word suggests.