How much eSIM data do you need in Korea?

How it’s calculated

Daily data = Σ(hours per activity × data per hour) + photo backup (photos × size per photo). A 20% buffer is added, and the result picks the first daily plan tier above it (0.5, 1, 2, 3 or 5 GB a day). Above 5 GB, it suggests unlimited.

Assumptions (data per hour)

The same activity can use very different amounts depending on settings, so every item has two values — typical and heavy — and the result is a range.

Activity	Typical	Heavy	What makes it heavy
Maps and navigation	5 MB	20 MB	Satellite or 3D view
Social media, messaging and web	91 MB	500 MB	Autoplaying video feeds
Video streaming	700 MB	3,000 MB	HD
Music streaming	72 MB	144 MB	Highest quality (320 kbps)
Video calls	540 MB	1,080 MB	720p HD
Hotspot for a laptop	91 MB	3,000 MB	The laptop streams video
Photo backup	2.3 MB per photo		HEIF. ProRAW is around 25 MB

Five of the six come from official help pages: Netflix, Spotify, Zoom and Apple for their own apps, and the UK carrier O2 for web browsing. Maps has no official figure, so it uses a blog post by Mint Mobile, a US carrier, and the result marks it as unofficial.

Maps vary the most. Plain navigation is 3–5 MB an hour, one figure for 3D immersive view is up to 600 MB, and the eSIM seller Airalo says 200 MB an hour for the same thing — a 40–60× spread for one item. This calculator uses the low end as the default and treats satellite view as “heavy”.

The plan suggestion uses the high estimate. Running out of data in a foreign city costs you more than paying for a little extra.

Examples

Example 1 — 5 days of sightseeing. Maps 2 h, social 2 h, video 30 min, 50 photos a day

Item	Calculation	Per day (typical)
Maps	2 h × 5–20 MB	10 MB
Social and web	2 h × 91–500 MB	182 MB
Video	0.5 h × 700–3,000 MB	350 MB
Photo backup	50 × 2.3 MB	115 MB
Per day		657 MB – 2.6 GB

With the 20% buffer on the high estimate, that is a 5 GB-a-day plan. Over 5 days it adds up to 3.2–13 GB.

Thirty minutes of video is 53% of the total. Two hours of maps is 10 MB; half an hour of video is 350 MB. Download your videos on hotel Wi-Fi instead, and the suggestion falls from the 5 GB to the 2 GB daily plan.

Example 2 — 5-day business trip. Hotspot 4 h, video call 1 h, social 2 h, maps 1 h

Item	Calculation	Per day (typical)
Maps	1 h × 5–20 MB	5 MB
Social and web	2 h × 91–500 MB	182 MB
Video calls	1 h × 540–1,080 MB	540 MB
Hotspot	4 h × 91–3,000 MB	364 MB
Photo backup	10 × 2.3 MB	23 MB
Per day		1.1 GB – 13.8 GB

At the high estimate that is 13.8 GB a day, beyond the daily tiers — unlimited is the right call.

The range spans 12× (1.1 to 13.8 GB). That is not a calculation error; it is how much real use varies. A laptop that only opens documents uses 91 MB an hour, and one in a video meeting can use 3,000 MB. If your trip means working from a laptop on a hotspot, don’t trust the low end — go unlimited.

From my own trips

I never skimped on data. Running out of data in the middle of a city you don’t know is about as frustrating as travel gets, so I always bought more than I thought I’d need. That is also why this calculator suggests plans from the high estimate.

But a bigger plan didn’t fix everything. More than once, a plan sold as “unlimited” was slower or patchier than I expected — few countries I visited had mobile internet as dependable as at home in Korea.

So once you’ve picked a data size, also look up which carrier network your eSIM runs on. How many gigabytes you buy and how fast they actually are are two separate questions. This calculator answers only the first.

What this calculator doesn’t cover

• Background app refresh and OS updates — data your phone uses on its own — aren’t included. The 20% buffer is there for that.