# Pond Calculator

URL: https://speedycalculator.com/calculators/construction/pond/
Last updated: 2026-10-25

> The pond calculator works out the water volume of a garden pond, the size of liner needed with overlap, the liner and fill cost, and the pump size to turn the water over once an hour.

## Inputs

- Shape
- Length (ft, m, in, yd, cm)
- Width (ft, m, in, yd, cm)
- Average depth (ft, m, in, yd, cm)
- Maximum depth (ft, m, in, yd, cm)
- Edge overlap (ft, m, in, yd, cm)
- Liner price (/ft², /m², /yd²)
- Water price (/1000 gal, /m³)

## Results

- Surface area
- Water volume
- Liner length
- Liner width
- Liner area
- Liner cost
- Water cost
- Pump size (1 turnover per hour)

## Formula

```
Volume = surface area × average depth
Liner length = L + 2 × max depth + 2 × overlap; liner width = W + 2 × max depth + 2 × overlap
Pump flow ≈ pond volume per hour
```

## Explanation

A flexible pond liner must cover the bottom, run up the sides at the deepest point and leave an overlap of about 1–2 ft around the edge to anchor under stones. A pump that circulates the whole volume roughly once every hour (every 2 hours for plant ponds, faster for koi) keeps water clear with a filter.

### How to use the Pond Calculator

- **Shape**
- **Length**
- **Width**
- **Average depth**
- **Maximum depth**
- **Edge overlap**
- **Liner price**
- **Water price**
- Every result field is editable: type into **Water volume** and **Average depth** plus every other field update to match.

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Choose the pond shape, enter the length, width, average and maximum depth, the edge overlap and prices for liner and water.

### Tips for an accurate estimate

- Measure inside dimensions of tanks and pools – wall thickness can change the volume noticeably.
- Use the average depth for pools with a sloping floor.
- Remember the weight: water weighs about 8.34 lb per US gallon (1 kg per litre), so large volumes need solid support.
- Check whether a figure is in US gallons, imperial gallons or litres before ordering chemicals or equipment.

### Common mistakes to avoid

- Using wall height instead of water depth for above-ground pools.
- Assuming a horizontal tank's volume is proportional to the liquid level – it is not.
- Mixing up flow units such as GPM, GPH and litres per minute.

### Inputs explained

FieldWhat to enterShapeChoose one: Rectangle, Oval / ellipse, Circle (length = diameter)LengthUnits: ft, m, in, yd, cmWidthUnits: ft, m, in, yd, cmAverage depthUnits: ft, m, in, yd, cmMaximum depthUnits: ft, m, in, yd, cmEdge overlapUnits: ft, m, in, yd, cmLiner priceUnits: /ft², /m², /yd²Water priceUnits: /1000 gal, /m³

### What each result means

- **Water volume** = [Surface area]×[Average depth]
- **Liner length** = [Length] + 2×[Maximum depth] + 2×[Edge overlap]
- **Liner area** = [Liner length]×[Liner width]
- **Liner cost** = [Liner area]×[Liner price]
- **Water cost** = [Water volume]×[Water price]
- **Pump size (1 turnover per hour)** = [Water volume]÷3600

### Example values

How the main result changes when **Average depth** changes and everything else stays at the example values above:

Average depth (ft)Water volume (US gal)14491.567328982.51,12231,34641,795

## Worked example

Inputs — Shape: Rectangle; Length: 10 ft; Width: 6 ft; Average depth: 2 ft; Maximum depth: 2.5 ft; Edge overlap: 1 ft; Liner price: $0.8 /ft²; Water price: $5 /1000 gal.

Results — Surface area = 60 ft²; **Water volume = 898 US gal**; Liner length = 17 ft; Liner width = 13 ft; Liner area = 221 ft²; Liner cost = $176.80; Water cost = $4.49; Pump size (1 turnover per hour) = 898 gph.

## FAQ

**How do I calculate pond liner size?**
Length + 2 × deepest depth + 2 × overlap, by width + 2 × deepest depth + 2 × overlap.

**How many gallons is my pond?**
Length × width × average depth (ft) × 7.48 for a rectangle; multiply by 0.785 for an oval.

**What size pump do I need?**
One that moves the whole volume about once an hour at the height you need to lift it.

**What formula does the Pond Calculator use?**
Volume = surface area × average depth.