Cloud storage is one of those subscriptions that people either wildly over-buy ("I'll get the 2TB plan, you never know") or perpetually under-buy, living in a state of chronic 95%-full notifications and desperate file deletion ceremonies. Neither approach is actually necessary. Your cloud storage needs can be calculated fairly precisely from the types of files you're storing and how quickly that collection grows over time. A little arithmetic now saves both wasted subscription money and the anxiety of running out of space at the worst possible moment.
The GB vs GiB Confusion (And Why Your Hard Drive Shows Less Space)
Before calculating storage needs, the units need clarifying. This is the source of the enduring mystery of why your "500 GB" hard drive only shows 465 GB when you plug it in.
Storage manufacturers measure in gigabytes where 1 GB = 1,000,000,000 bytes (powers of 10). Operating systems and file systems measure in gibibytes (GiB) where 1 GiB = 1,073,741,824 bytes (powers of 2). The same physical storage measures differently depending on which standard you apply.
500 GB (manufacturer) ÷ 1.073741824 = 465.7 GiB (what Windows or macOS displays). Your drive isn't shortchanging you — it's a unit conversion. Use our data storage converter to translate between GB, GiB, TB, TiB, and all other storage units accurately. Cloud storage services (iCloud, Google One, Dropbox) typically quote in GB (decimal), so a 200 GB iCloud plan holds 200 × 10⁹ bytes — slightly less than 200 GiB in gibibyte terms, though the difference is modest at typical storage plan sizes.
Estimating Your Document and Email Storage
For most office workers, document, spreadsheet, and email storage is surprisingly modest. Typical file sizes:
- Word document (text only, 10 pages): 30–80 KB
- Excel spreadsheet (moderate complexity): 100–500 KB
- PDF (standard quality, 10 pages): 500 KB–2 MB
- PowerPoint presentation (with images): 2–15 MB
- Email with attachments: 1–10 MB per email
A prolific document creator might accumulate 5,000 documents over a year. At an average of 500 KB each: 5,000 × 500 KB = 2,500,000 KB = 2.5 GB per year. Email storage varies enormously; 10 GB per year would be a heavy email user. Documents alone rarely drive cloud storage requirements into the tens or hundreds of gigabytes — photos and videos are almost always the driving factor.
Photo Storage: The Real Culprit
Modern smartphone cameras produce large files. Typical photo file sizes in 2026:
- Standard JPEG from smartphone: 3–6 MB
- HEIC (iPhone default format): 2–4 MB (more efficient than JPEG)
- RAW file from DSLR or mirrorless: 20–50 MB
- Burst photos and Live Photos: additional storage overhead
A family taking 4,000 photos per year (roughly 11 per day — quite moderate) at an average of 4 MB each: 4,000 × 4 MB = 16,000 MB = 16 GB per year. Over five years without any deletions: 80 GB of photos alone. This is why iCloud's free 5 GB tier becomes inadequate remarkably quickly for any active smartphone user.
Use our file size calculator to estimate total storage for your photo library based on file count and average size, or to compare storage requirements for different shooting formats (JPEG vs HEIC vs RAW).
Video Storage: Orders of Magnitude Larger
Video files dwarf photo storage requirements. Typical video file sizes:
- 1 minute of 1080p video (smartphone, HEVC): 50–100 MB
- 1 minute of 4K video (smartphone, HEVC): 150–400 MB
- 1 minute of 4K ProRes (iPhone Pro): 3–6 GB
- A 2-hour film (streaming quality): 4–10 GB
Even moderate video recording adds up fast. Recording 30 minutes of 4K video per month: 30 × 300 MB = 9 GB/month, or 108 GB/year. A 2TB cloud plan starts to look sensible once video recording is part of the picture — or selective deletion/offloading to local storage becomes necessary.
Choosing the Right Storage Tier
Work through this calculation: estimate your annual photo volume (count × average file size), add video if applicable, add document storage, then multiply by how many years you want to retain without managing deletions. This gives you the total storage required for passive accumulation.
Common cloud storage services in 2026 offer tiers at roughly: 15–20 GB free; 50–100 GB at £1–£2/month; 200 GB at £2–£3/month; 2 TB at £7–£10/month. For most individuals without heavy video recording, 200 GB–1 TB is adequate. Families sharing a plan, photographers, and videographers typically need 2 TB or more.
Consider also whether you need the storage continuously accessible (cloud sync for active use) versus long-term archival (cold storage is significantly cheaper per GB for files you rarely access). Backblaze B2, Amazon Glacier, and similar services offer archival rates well below primary cloud storage pricing.
Wirecutter's guide to best cloud storage services provides regularly updated comparisons of pricing, features, and reliability across the major providers.