Free calculator
Pond Volume Calculator
Estimate pond water capacity from shape and average depth in litres, cubic metres and UK imperial gallons.
Open calculator →Garden project hub
Ponds & water
Water volume and liner dimensions use different depth measurements, so the two pond calculators deliberately do not share one formula.
Use the right quantity tool
Calculators for ponds & water
Keep pond capacity, liner sheet size and rainwater storage as distinct planning questions.
Free calculator
Pond Liner Calculator
Estimate liner length, width and area from maximum dimensions, maximum depth and an editable edge allowance.
Open calculator →Free calculator
Water Butt Calculator
Compare roof rainfall yield, storage, fill rainfall and garden watering demand without treating annual yield as tank size.
Open calculator →Before you order
Keep the project decisions separate from the arithmetic
Pond volume uses average depth
Water capacity should reflect the pond as a whole. Using the deepest point for every square metre can substantially overstate volume when shelves or slopes are present.
Pond liner uses maximum depth
The sheet must travel down and back up the deepest section, so liner sizing works from maximum length, maximum width, maximum depth and an explicit edge allowance.
Rainwater storage is a different system
A water butt calculation starts from roof catchment and rainfall. It belongs in the wider water topic but should never be mistaken for pond capacity or liner sizing.
Supporting guidance
Read the guide when the difficult part is choosing the input
Practical guide
Pond Volume & Liner Measuring Guide
Use average depth for water capacity and maximum depth for liner sizing without mixing the two jobs.
Read guide →
Practical guide
What Size Water Butt Do I Need?
Think about roof catchment, rainfall timing, storage turnover and garden demand before choosing capacity.
Read guide →Continue the project
Useful next routes
Move to the next quantity only when it describes a genuinely different part of the job.
Pond measuring guideSee why average depth and maximum depth belong to different calculations.Watering & rainwaterMove from captured rainfall into garden demand and irrigation runtime.Volume conversionsCheck litres, cubic metres and UK imperial gallons.Calculation methodologySee how exact geometry and approximations are labelled across the site.