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Oil Tank Sizing Calculator

Get a quick capacity estimate for your home from a few details. It's a starting point — every property is different, so a free site survey confirms the exact size and position.

Estimated requirement

Based on typical 2026 UK usage, your property likely needs:

1,200 – 1,500 litres
Recommended tank typeBunded plastic
Approx. weight when full~1.5 tonnes

This is an estimate only. We recommend a free site survey for an exact recommendation.

Choosing the right capacity matters. A tank that's too small leads to frequent, expensive deliveries and the risk of running dry in a cold snap. One that's too large takes up valuable garden space and needs a bigger structural base. The calculator above uses the industry "500 litres per bedroom" rule of thumb as a starting point — but your actual usage, insulation and available space all shape the real answer.

📐 The 500L-per-bedroom rule: allow roughly 500 litres per bedroom plus 500 litres for general hot water and living space. A 3-bedroom home lands around 1,200–1,500 litres.

Standard capacities for UK homes

  • 1–2 bedrooms: 650 – 1,000 litres (ideal for slimline tanks in tight garden spots).
  • 3–4 bedrooms: 1,200 – 1,800 litres (the most common domestic size).
  • 5+ bedrooms: 2,000 – 2,500+ litres (may require larger or multiple tanks).

Our oil tank sizes guide shows the relative dimensions, and how to choose the right size walks through the full decision.

The "AGA effect"

If your home has an oil-fired AGA or Rayburn for cooking, fuel consumption rises by roughly 20–30%. The calculator accounts for this by suggesting a larger capacity so you aren't calling for deliveries every few months.

Bunded vs single-skin

A bunded tank is a tank within a tank — if the inner tank splits, the outer skin (the bund) captures the leak. It's mandatory for tanks over 2,500 litres, for tanks near a river, stream or borehole, and wherever a leak could reach a drain. Many insurers now require a bunded tank regardless of size, which is why we recommend bunded for most homes. Our regulations guide covers the location rules in full.

Weight and base requirements

Heating oil weighs about 1 tonne per 1,000 litres. With the tank itself, a full 1,500-litre tank puts over 1.6 tonnes on the ground, so a compliant base matters:

  • Thickness: concrete bases should be at least 100mm thick.
  • Footprint: the base must extend at least 300mm beyond the tank in all directions.
  • Material: non-combustible and completely level.

Our team provides full base and compliance work as part of every installation.

Calculator FAQs

What size tank do I need for a 3-bedroom house?

For a standard three-bedroom house we typically recommend 1,200–1,500 litres, allowing roughly one large delivery a year with a buffer for cold winters.

Is there a ban on oil tanks in 2026?

No. The Future Homes Standard applies only to new-build properties. If you live in an existing oil-heated home, you can replace your tank, service your boiler or install a new oil-based system.

How far must my tank be from the house?

Generally 1.8 metres from non-fire-rated structures such as doors or windows. Where space is limited, a fire-rated barrier can reduce this distance safely. See our regulations guide.

How long does a modern oil tank last?

A quality UK-made bunded plastic tank has an expected lifespan of around 20 years, and most installs come with a warranty of up to 10 years.

Ready for an Exact Sizing Assessment?

Serving Salisbury, Swindon, Chippenham, Trowbridge, Devizes, Marlborough and all surrounding villages. Drop us a message for a free survey and fixed quote.

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