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You’ll likely agree with us when we say that trying to estimate how much water your pond can hold is very difficult.

Use our pond volume calculator to help! 👍

Keep reading this article to see just how easy it is to use.

We will also explain the Mathematics the calculator uses to estimate out how much water your pond can hold.

Contents:

To calculate the total volume of your pond, you must first measure the dimensions of your pool.

These can be in **metric units** (centimeters or meters) or **imperial units **(yards, feet or inches).

The calculator then works out the total volume of the pond using the following formulae:

For a rectangular pond, the **surface area** is calculated by:

$$Surface\,Area = Length × Width$$

and the **total volume **is calculated by:

$$Volume = Surface\,Area × Depth$$

As a general rule, the **total volume **of an irregular pond is a third smaller than a rectangular pond.

We therefore take the volume of the rectangular pond:

$$Volume = Length × Width × Depth$$

and multiply by 2/3 to get the **total volume **of an irregular pond:

$$Volume= {2 \over 3} × Length × Width × Depth$$

In addition, the **surface area **of an irregular pond is 15% less than a rectangular pond. Therefore:

$$Surface\,Area = Length × Width – 15\%$$

For a circular pond, the **surface area **is calculated using the formula:

$$Surface\,Area= \pi × Radius^2$$

where

$$Radius = {Width \over 2}$$

and **total pond volume **is calculated by**:**

$$Volume = Surface\,Area × Depth$$

For an oval pond, the **surface area **is calculated using the formula:

$$Surface\,Area= \pi × {Width \over 2} × {Length \over 2}$$

and **total pond volume** is calculated by**:**

$$Volume = Surface\,Area × Depth$$

Note that a circle is an oval with equal length and width!

The calculator gives answers for volume in liters, US or UK gallons, whereas the above calculations will give the answers in **cubic feet. **

Therefore, we need simply do the following conversions:

$$1\,ft^3 = 7.48\,US\,gallons$$

$$1\,ft^3 = 6.23\,UK\,gallons$$

$$1\,ft^3 = 28.32\,litres$$

Note that these are not exact conversions. However, the calculator does the exact conversions for you, so you don’t need to worry. 😉

A liner is a waterproof material that sits at the bottom of the pond. Its primary purpose is to ensure the pond remains watertight.

Imagine you have an irregular pond like this:

We must allow for a “safety overlap” of 2 feet.

This helps us ensure that we have sufficient material to account for any mistakes in measuring etc.

The liner has dimensions:

$$Liner\,Length = Pond\,Length + Depth × 2 + 2\,feet$$

$$Liner\,Width = Pond\,Width + Depth × 2 + 2\,feet$$

We have to include the depth twice to account for the liner running from the top to the bottom of the pond and then from the bottom back to the top (i.e. **twice**).

Note:If you are using an irregular pond, then you should always use themaximum pond length and widthin these calculations to ensure you have sufficient liner.

Ensuring you purchase a pump of sufficient size is crucial to your pond’s success.

It is recommended that you purchase a pump that circulates** at least** 50% of the ponds total volume **every hour.**

Therefore:

$$Minimum\,Pump\,Size = {Pond\,Volume \over 2}$$

**Confused? 😕**

See below for three fully worked examples where we calculate the **surface area **and **volume **of several ponds.

We will also show you how to calculate the **liner size** and recommend a **minimum pump size** for the given ponds.

Otherwise, simply enter your measurements into our online pond calculator!

**Rectangular Fish Pond**

Imagine my fish pond measures 10 feet in length, 12 feet in width and the bottom of the fish pond is at a constant depth of 5 feet.

I would enter these values into the pond calculator to work out the **surface area:**

$$Surface\,Area = Length × Width = 10\,ft × 12\,ft = 120\,ft^2$$

and the **total volume** of the fish pond:

$$Volume = Surface\,Area × Depth = 120\,ft^2 × 5\,ft = 600\,ft^3$$

If I want to calculate the volume in US gallons, I would use the conversion:

$$1\,ft^3 = 7.48\,US\,gallons$$

Therefore

$$600\,ft^3 = 4488.31\,US\,gallons$$

Now, to calculate the **size of the liner** required for the fish pond:

$$Liner\,Length = Pond\,Length + Depth × 2 + 2\,feet = 10 + 5 × 2 + 2 = 22\,ft$$

$$Liner\,Width = Pond\,Width + Depth × 2 + 2\,feet = 12 + 5 × 2 + 2 = 24\,ft$$

Finally, to calculate the recommended **minimum pump size:**

$$Minimum\,Pump\,Size = {Pond\,Volume \over 2} = {4488.3 \over 2} = 2244.15\,US\,gal/h$$

**Irregular Pond**

Now, let’s imagine that we have an irregular pond shape.

The maximum width is 17 feet, and the maximum length is 12 feet.

Therefore, the **surface area** of the pond is:

$$Surface\,Area = Length × Width – 15\% = 17 × 12 – 15\% = 173.4\,ft^2$$

Note, to calculate a reduction of 15%, simply multiply by 0.85.

Now, let’s imagine the maximum depth of the pond is 10 feet.

The **volume **of the irregular pond can be calculated by:

$$Volume = {2 \over 3} × Length × Width × Depth = {2 \over 3} × 17\,ft × 12\,ft × 10\,ft = 1360\,ft^3$$

Let’s say that I want to calculate the volume in litres. Recall that:

$$1\,ft^3 = 28.32\,litres$$

Therefore:

$$1360\,ft^3 = 38510.9\,litres$$

Now, to calculate the **size of the liner** required for the pond is:

$$Liner\,Length = Pond\,Length + Depth × 2 + 2\,feet = 12 + 10 × 2 + 2 = 34\,ft$$

$$Liner\,Width = Pond\,Width + Depth × 2 + 2\,feet = 17 + 10 × 2 + 2 = 39\,ft$$

Finally, to calculate the recommended **minimum pump size:**

$$Minimum\,Pump\,Size = {Pond\,Volume \over 2} = {38510.9 \over 2} = 19255.5\,litres/h$$

**Oval Fish Pond**

For our final example let’s imagine I want to know an estimate of how many **US gallons** of water it will take to fill an oval fish pond measuring 30 feet in width, 25 feet in length and 12 feet deep. The pond gallons calculator first figures out the **surface area:**

$$Surface\,Area= \pi × {Width \over 2} × {Length \over 2} = \pi × {30\,ft \over 2} × {25\,ft \over 2} = 589.049\,ft^2$$

and then the **total volume **of the fish pond:

$$Volume = Surface\,Area × Depth = 589.049\,ft^2 × 12\,ft = 7068.58\,ft^3$$

Then, to convert this into **US gallons, **recall that one cubic foot is equivalent to 7.48 US gallons. Therefore, we have:

$$7068.58\,ft^3 = 52876.68\,US\,Gallons$$

Now, to calculate the dimensions of the **required total liner** we must use the **maximum length and width** of the fish pond:

$$Liner\,Length = Pond\,Length + Depth × 2 + 2\,feet = 30 + 12 × 2 + 2 = 56\,ft$$

$$Liner\,Width = Pond\,Width + Depth × 2 + 2\,feet = 25 + 12 × 2 + 2 = 51\,ft$$

**Be careful!**

It’s important that you don’t round your answers too early!

Don’t round your answers until the **very last calculation **to ensure accuracy throughout the calculations**.**

Using our pond calculator will help you with this J

Finally,

The online pond calculator does the conversions for you.

All you need to do is select the desired units in the drop down option and the calculator will do the following conversions for you:

$$1\,foot = 12\,inches = 0.33\,yards = 30.48\,centimeters = 0.3048\,meters$$

$$1\,ft^2 = 144\,in^2 = 0.111\,yd^2 = 929\,cm^2= 0.0929\,m^2$$

It couldn’t be simpler! 🙂