Free pond sealer calculator
Pond Sealer Calculator
For rendered concrete or block ponds sealed without a liner. Enter the length, width and depth to see how much pond sealer you need for the full three-coat system, with the cheapest mix of 1kg, 2.5kg and 5kg tins. Metric or imperial.
Lining a block or concrete pond instead? Use the pond liner calculator →
Pond sealer questions
How do I calculate what size pond liner I need?
Liner length = pond length + (2 × maximum depth) + 0.6m, and liner width = pond width + (2 × maximum depth) + 0.6m. The 0.6m gives a 30cm edge on every side. A 3m × 2m pond 0.6m deep needs at least 4.8m × 3.8m, so choose 5m × 4m.
How much edge overlap do I need?
30cm on each edge is standard. Allow 50cm if you are finishing with paving or rocks, and add the depth and width of an anchor trench if you use one.
Do pond shelves need extra liner?
No. Size from the maximum depth and the shelves are covered. Shelves do reduce the water volume, which the planner allows for.
What size pump do I need?
Turn the pond volume over about every 2 hours for ornamental and goldfish ponds and every hour for koi, then allow extra for pipework and any waterfall height. Wildlife ponds do not need a pump.
What size filter do I need?
Choose a filter rated for more than your pond volume: about 1 × for plant ponds, 1.5 × for goldfish and 2 × for koi, and size up again for a pond in full sun.
How much pond sealer do I need for a concrete pond?
Work out the inside area (floor plus walls) and multiply by 0.55kg per m² for three coats of clear pond sealer. A 3m × 2m × 1m pond has 16m² inside, so it needs about 8.8kg.
How much underlay do I need?
Order underlay in the same size as the liner. If you join pieces, overlap them by at least 300mm.
How much pond sealer do I need?
Work out the inside area of the pond, the floor plus every wall, then multiply by 0.55kg per m². That covers the full three-coat system of PondLinersco Clear Pond Sealer, so a 1kg tin seals about 1.8m².
Sealer needed (kg) = (floor area + wall area) × 0.55
| Pond (length × width × depth) | Floor + walls | Sealer needed |
|---|---|---|
| 1m × 1m × 0.5m | 3m² | about 1.7kg |
| 2m × 1.5m × 0.6m | 7.2m² | about 4kg |
| 3m × 2m × 1m | 16m² | about 8.8kg |
| 4m × 3m × 1.2m | 28.8m² | about 15.8kg |
Planting shelves and sloping sides add wall area, so the calculator allows 15% extra for shelves and 25% for sloping sides.
How to apply it
- Let new concrete or render cure for at least 28 days, then clean off dust, loose material and algae and fill any cracks.
- Brush on the first coat, working it into joints and corners.
- Recoat after 60 to 90 minutes. Never leave more than 4 hours between coats, so each coat bonds to the last.
- Apply the third coat the same way, let it cure fully, then fill, empty and refill the pond before adding fish.
Pond sealer is for concrete, render, brick and stone only. It is not compatible with PVC, butyl rubber or bitumen, so never use it on a pond liner. Full instructions: how to seal a concrete pond.