One of the confusing things about buying a new device is choosing how much storage to get. Even once you’ve decided which model iPhone or iPad you want, you’ll still need to decide whether the base capacity is enough for your needs or if you’re better off paying extra for more storage space.

iPhones 8, 8 Plus and X give you two options: 64GB or 256GB. Older iPhones offer a choice between 32GB and 128GB, while most of the iPad range is even more convoluted, with a range of options from 32GB to 512GB depending on the exact model. It’s pretty confusing for the average customer.

The higher capacity models, of course, come with a significant bump to the cost. It’s a system that makes it easy for Apple to upsell customers, but how can you be sure how much storage you really need?

Choosing a new iPad can be a real headache…

As a general rule, heavier users will normally want to plump for the extra storage. Apps, games, photos, videos, music – all these things take up space on the device and it doesn’t take much to fill up the base tier. On the flip side, those who mainly use their devices to send messages, check emails, and browse the internet will probably be fine with the cheaper options.

It’s also worth remembering that streaming music and videos from services like Spotify and Netflix doesn’t use up permanent storage space, but downloading media for offline use does.

If you want a more scientific approach to decision-making, though, we’ve got a sure-fire way to see how much space you’ll need. It’s simple, really: see how much space you’re already using on your current device.

To do this, open the Settings app on your device and press GeneraliPhone Storage (or iPad Storage). At the top of this screen, it’ll show how many gigabytes (GB) you’re currently using.

Plenty of room on a 256GB device, but all these apps would never fit on the entry-level iPhone

Use this as a guide when upgrading to a new device: any storage capacity smaller than you’re currently using will feel like a downgrade. If you’re forever deleting apps and photos to make room for new ones, we’d recommend you get the next tier up when you buy a new device. Conversely, if you’re only using 15GB right now then there’s no point wasting money on a 256GB device, is there?