iPhone Storage Size Calculator
Choose your iPhone model, enter how much storage you use now and expected future growth, and find the smallest available iPhone storage size that meets your needs and free-space buffer.
Last updated: July 2026
Find the smallest storage tier that fits
Recommended storage
Compare every available storage tier
Start with how much storage you use now
Check the storage currently used under Settings > General > iPhone Storage. Add only the extra local storage you expect before your next upgrade. This is more personal than guessing from a generic light or heavy user profile.
How the recommendation works
Projected use = Current storage used + Expected extra storage.
Minimum capacity = Projected use / (1 - Free-space buffer).
The calculator selects the smallest real storage tier for the chosen iPhone that meets that minimum. For example, 200 GB of projected use with a 20% buffer requires 250 GB, so an iPhone 17 is matched to its 256 GB tier.
Why free space matters
Buying capacity equal to projected use leaves no room for updates, downloads, temporary data, new apps, or unexpected growth. The buffer is your planning choice; it is not presented as a universal Apple recommendation.
Advertised capacity versus available storage
Apple markets storage in decimal units, so this calculator uses 1 TB = 1000 GB and 2 TB = 2000 GB. Formatting, iOS, built-in resources, apps, and system data consume some capacity, so this is a planning tool rather than a prediction of the exact free-storage figure shown by iOS.
iCloud and local iPhone storage are different
iCloud is cloud storage; it does not change the physical storage tier built into the phone. If streaming, optimized photos, or regular offloading will reduce your expected local use, reflect that in the storage estimate you enter.
Frequently asked questions
How much iPhone storage do I need?
Enter current use, expected extra local storage, and a free-space buffer. The calculator selects the smallest qualifying tier sold for the chosen iPhone.
Is 256GB enough for an iPhone?
It depends on projected local use. The tool checks 256 GB against both your data and your selected spare-space buffer.
Should I buy 256GB or 512GB?
The smaller tier is recommended only when it holds projected storage while maintaining your selected buffer.
Does iPhone 17 come in 128GB?
No. This calculator's iPhone 17 preset exposes only 256 GB and 512 GB.
Can I use this for an older iPhone?
Yes. Choose Other / Custom iPhone to compare the generic 64 GB, 128 GB, 256 GB, 512 GB, 1 TB, and 2 TB tiers. Not every older iPhone was sold in every one of those capacities.
Apple and iPhone are used descriptively. This site is not affiliated with or endorsed by Apple.