Offline music storage calculator

How this works

Three numbers go in: how many tracks, what format they’re in, and how much space the phone has free right now. The first two give the size of the library once it’s on the device; the third decides whether that size is comfortable, a decision, or simply too big. Those are the three outcomes the guide describes, and the tool never adds a fourth.

It also never picks a player. Storage is the one part of choosing an offline music player that doesn’t depend on which player you choose — a 10 GB library is 10 GB in every app that copies files onto the phone — so a calculator that ended with a recommendation would be smuggling in a claim it hadn’t earned. When a library doesn’t fit, the honest routes are to import less of it or to reach it from a drive, and the second of those points at a player that isn’t ours.

Where the numbers come from

Every per-track figure is from the storage section of our own best offline music player apps guide, and they’re rounded there on purpose, because bitrates vary within a library and a decimal point would be false precision.

Three things on this page are ours rather than the guide’s, and the result labels each one where it uses it. The 256 kbps row is the same arithmetic — bitrate times seconds, divided by eight — run for the rate most download stores sell at, because a lot of libraries are store purchases and the guide doesn’t quote a figure for them. The track-length options scale the per-track figure in a straight line, which is what bitrate means. And the line between “fits, with room” and “fits, but it’s a decision” is drawn where the library would take more than half of what’s free, or leave under 5 GB — our reading of the guide’s example, where 10 GB on a 128 GB phone is comfortable and 35 GB is a decision, translated from the size of the phone to the space actually left on it.

Sizes are decimal gigabytes, the same unit the iPhone Storage screen uses, so the figure you type in and the figure that comes out are comparable without a conversion.

If you’re not sure, assume the library is bigger

The two mistakes aren’t symmetrical. Overestimating costs you nothing — you import a little less than you could have, or you check one file’s size in the Files app and come back. Underestimating costs an afternoon: a few hundred tracks imported, a phone that’s suddenly full, and the same tracks deleted again one album at a time. So where the tool has to guess, it guesses large: an unknown format is costed at 320 kbps rather than 128, and a lossless library is judged on the 40 MB end of the range rather than the 30.

If you don’t know the format, one file settles it. Long-press a song in the Files app and tap Get Info: a four-minute song near 4 MB is 128 kbps, near 10 MB is 320, and anything over 25 MB is lossless.

• The best offline music player apps for iPhone & iPad — the guide these figures come from, and the five players sorted by job
• Music format check — storage is half the question for FLAC and ALAC; this is the other half: which player actually reads what you own
• How to listen to music without ads on iPhone — the three routes, and why a file on the phone is the only one with no ad slot attached
• Doppler alternatives — if the lossless library is the point and you’re choosing between the players that keep it