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Imperial Gallons to Litres Calculator

Convert UK imperial gallons to litres for tank ratings, older plant and pre-metric specifications.

  • Answers as you type
  • Every formula cited
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Market
Imperial · sales tax
The volume in imperial (UK) gallons.

Check first that the figure really is imperial rather than US. British plant, cold water storage cisterns and anything specified before metrication use the imperial gallon; equipment imported from North America almost always means the US one, which is about a fifth smaller.

Volume

227.3 L

High confidence

1 imperial gallon = 4.54609 L exactly, as defined in the Weights and Measures Act 1985. Exact by definition — but confirm the source figure is imperial and not a US gallon before converting it.

Same volume in US gallons
60.05 US gal
Same volume in cubic metres
0.23 m³
Then change the inputs to see how far the answer moves.

Show calculation logic

How this was calculated

Formula source(s)

  • Weights and Measures Act 1985 (UK): 1 imperial gallon = 4.54609 litres exactly
  • NIST Handbook 44, Appendix C: 1 US liquid gallon = 231 in³ = 3.785411784 L exactly

Inputs used

Volume (imp gal)
50

Intermediate steps

Same volume in US gallons
60.05 US gal
Same volume in cubic metres
0.23 m³
Final result227.3 L

Confidence note: 1 imperial gallon = 4.54609 L exactly, as defined in the Weights and Measures Act 1985. Exact by definition — but confirm the source figure is imperial and not a US gallon before converting it.

Estimated cost — your price

This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.

Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.

Sources checked 2026-09-11 · v1.0.0

Regulatory standards & verification citations2
  1. Weights and Measures Act 1985 (UK): 1 imperial gallon = 4.54609 litres exactly
  2. NIST Handbook 44, Appendix C: 1 US liquid gallon = 231 in³ = 3.785411784 L exactly
Cite this page

Your workspace

Most jobs need more than one number. Add the calculators you need next and they open right here, underneath this one — your figures stay on screen and nothing is lost to a page change.

Britain has been metric for trade since 2000 and is still full of equipment rated in imperial gallons, which is precisely why this conversion matters more than its arithmetic suggests. The risk is not in the factor, it is in the word: "gallon" on a nameplate means two different volumes twenty percent apart, and nothing on the plate usually says which. A storage tank, a bowser, an expansion vessel or a fuel figure read as the wrong gallon is out by a fifth in the direction that runs you short. Establish the nationality of the unit first, then convert — and remember that a rated capacity and a usable capacity are not the same number either.

Called something else where you work? Gallon — the term in each market, how close the equivalence really is, and the standard that governs it.

How to calculate imperial gallons to litres in 2 steps

  1. Volume (imp gal)The volume in imperial (UK) gallons.
  2. VolumeThe tool computes the volume from those figures and shows the formula, its sources, and a confidence rating alongside it.

Imperial Gallons to Litres at common values

Page defaults, not your figures above.

Volume (imp gal)Volume (L)
522.7
1045.5
2090.9
50227
100455
200909
5002,273

Frequently asked questions

How different is an imperial gallon from a US one?
Substantially — 4.546 litres against 3.785, so the imperial gallon is about twenty percent larger. On a 50 gallon rating that is nearly 38 litres of difference, which is the whole margin on a storage calculation. A bare "gallons" on a rating plate with no nationality attached is a figure to chase down rather than convert.
Where does the imperial gallon still turn up?
On the rating plates of older British tanks and cisterns, in pre-metrication drawings and specifications, in fuel economy quoted as miles per gallon, and in the capacities of plant that has been in service for decades. It has not been a legal unit for trade in the UK since 2000, but the equipment and the paperwork long outlive the legislation.
Is 4.54609 exact or a rounded figure?
Exact, by definition, and it has been since 1985. Before that the gallon was defined physically as the volume of ten pounds of distilled water weighed in air at a stated temperature and pressure, which came out at a slightly awkward number; the 1985 Act replaced that with the round metric definition used today.
Does a tank actually hold its rated capacity?
Rarely all of it. A cistern's rated capacity is usually the nominal or brim-full volume, while the working volume is set by the overflow and the float valve, and on a cold water storage cistern that can be a tenth or more below the rating. Convert the number on the plate, then find out which volume the plate is describing before you rely on it.
Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — a confirmed fix gets a permanent check of its own, so the same mistake cannot come back.