Water Butt Size Calculator

full water butt
full water butt


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What size water butt should I buy?

This is a common question asked by people when considering purchasing a water butt. The challenge is how to calculate the water butt size for their garden. The answer will vary on many factors including the weather and the watering requirements of their plants.

On this page I’ve provided two look up tables to help calculate the water butt size required, and perhaps, help discover if more than one water butt is needed. The simple answer is that the water butt(s) will need to store enough water to last until the next rain shower that replenishes it. Therefore the water butt size you need depends upon:

  • How much water you use a day
  • How frequently it rains

To use the water butt size calculator tables you will need to know:

  • How many watering cans you typically use a day
  • The size of watering can you use

The tables will then show you how many days a full water butt will last until the next rainfall.

Please note these water butt size calculator tables are an approximation – I have not tried to work in possible evaporation rates etc. The intention is to provide enough information to enable you to quickly see the amount of water you need to store based on your watering needs.

100 Litre Water Butt Size Calculator

100 litre water butt size calculator table

200 Litre Water Butt Size Calculator

200 litre water butt size calculator table

Based on the tables above, if you have a large number of plants or pots you may find that one water butt alone will not meet your needs during a period of dry hot weather. Many people opt to link water butts together for this reason.

Buying large capacity water butts, ie water butts greater than 200 litres, is usually significantly more expensive that buying multiple standard size water butts.

See water butts in the shop.

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