Outdoor and hobby calculators
Calculators for garden and outdoor hobbies where getting a number wrong costs money or breaks a rule: dosing a pond, buying a liner, checking an air rifle is legal, or registering a drone under the 2026 CAA rules.
- Pond volume calculatorLitres, liner size and pump flow for a garden pond.
- Air rifle muzzle energy calculatorFoot-pounds from pellet weight and speed, checked against the UK limit.
- Drone registration checkerWhether you need a Flyer ID, an Operator ID or both under the 2026 rules.
The figures these tools use
| What | Figure | Source |
|---|---|---|
| Pond liner | Length or width + 2 × depth + 1m | Hozelock |
| Koi pond pump | Whole volume once an hour | Pondkeeper |
| Air rifle limit | 12 ft lb (pistol 6 ft lb) | legislation.gov.uk |
| Drone Flyer ID | Needed from 100g since 1 January 2026 | CAA |
| CAA Operator ID | £12.34 a year | CAA |
Checked on 25 October 2026. How we calculate explains the method behind each tool.