Before buying a drive, sizing a backup target, or provisioning a cloud bucket, you need a realistic total. This calculator turns a file count and an average file size — plus optional headroom — into a total shown in MB, GB, and TB.
How it works
The estimate is a single product:
total = number of files × average file size × (1 + headroom%)
The average size is converted from your chosen unit (MB, GB, or TB) before multiplying, and the result is shown across all three units using decimal sizing (1 GB = 1000 MB, 1 TB = 1000 GB) — the same convention drives are advertised under, so the figure maps straight onto what you would purchase.
The headroom percentage covers growth and the fact that filesystems reserve space for metadata and never fill to 100%.
Example
5000 photos averaging 4 MB each, with 20% headroom:
- Base = 5000 × 4 = 20,000 MB = 20 GB
- With headroom = 20,000 × 1.2 = 24,000 MB = 24 GB
| Quantity | Value |
|---|---|
| Files | 5000 |
| Average size | 4 MB |
| Base total | 20 GB |
| Headroom | 20% |
| Total needed | 24 GB |
Everything is calculated locally in your browser, with nothing sent anywhere.