Reference

UK Coin Sizes and Weights: Every Coin in mm and Grams

A 1p is 20.3 mm across, a 2p 25.9 mm, a 5p 18 mm, a 10p 24.5 mm, a 20p 21.4 mm, a 50p 27.3 mm, a £1 23.43 mm and a £2 28.4 mm. The table below gives the diameter, thickness, weight and metal of every coin in circulation, using the Royal Mint’s published specifications.

Reviewed by Connor Jones, Editor Last updated:
In brief. The £2 is the biggest and heaviest UK coin in circulation (28.4 mm, 12 g). The 5p is the smallest (18 mm, 3.25 g). Got an unknown coin? Measure it and use the diameter identifier, or weigh it and use the weight identifier.
Explains UK coin sizes and weights, e.g. why the 2p is big (Atomic Shrimp) Video: Atomic Shrimp on YouTube

UK coins in circulation

CoinDiameterWeightThicknessMetal
1p
1971 to date		 20.30 mm 3.56 g 1.52 (bronze) / 1.65 (steel) mm Bronze to 1992, copper-plated steel since
2p
1971 to date		 25.90 mm 7.12 g 1.85 (bronze) / 2.03 (steel) mm Bronze to 1992, copper-plated steel since
5p
1990 to date		 18.00 mm 3.25 g 1.70 mm Cupro-nickel to 2011, nickel-plated steel since 2012
10p
1992 to date		 24.50 mm 6.50 g 1.85 mm Cupro-nickel to 2011, nickel-plated steel since 2012
20p
1982 to date		 21.40 mm 5.00 g 1.70 mm Cupro-nickel (84% copper, 16% nickel)
50p
1997 to date		 27.30 mm 8.00 g 1.78 mm Cupro-nickel (75% copper, 25% nickel)
£1 (12-sided)
2017 to date		 23.43 mm 8.75 g 2.80 mm Nickel-brass outer, nickel-plated alloy inner
£2
1997 to date		 28.40 mm 12.00 g 2.50 mm Nickel-brass outer, cupro-nickel inner

The 20p and 50p are seven-sided curves of constant width, so they measure the same across any two opposite points and still work in vending machines.

Why two coins of the same value can differ

Vernier caliper of the kind used to measure a coin's diameter
Image: Mahr Mar Cal 16 N vernier caliper by Lucasbosch, Wikimedia Commons, licensed under CC BY-SA 3.0

In September 1992 the 1p and 2p switched from bronze to copper-plated steel, and in January 2012 the 5p and 10p switched from cupro-nickel to nickel-plated steel. The diameter and weight stayed the same, but the steel coins are slightly thicker and they stick to a magnet. That magnet test is the quickest way to tell a bronze 1p or 2p from a steel one. In 1992 (and again in 1998 for the 2p) both alloys were struck, so the date alone will not tell you. See the 2p coin values guide for the dates that do carry a premium.

Old and withdrawn coins

Engraving of a precision balance used for weighing small items such as coins
A precision balance gives accurate coin weights.Image: EB 1911 Weighing Machines - Precision Balance by Unknown author, Wikimedia Commons, Public domain
CoinDiameterWeightNotes
Large 5p
1968 to 1990		 23.59 mm 5.65 g Withdrawn 31 December 1990
Large 10p
1968 to 1992		 28.50 mm 11.31 g Withdrawn 30 June 1993
Large 50p
1969 to 1997		 30.00 mm 13.50 g Demonetised 1998
Round £1
1983 to 2017		 22.50 mm 9.50 g Demonetised 15 October 2017; 3.15 mm thick

The large 5p and 10p were the same size as the shilling and florin they replaced, which is why those pre-decimal coins stayed in use until 1990 and 1993. For gold coins, see the sovereign weight and specifications guide. For shillings, florins and crowns, see the pre-decimal coins guide.

Identify a coin by size or weight

A small group of UK coins lying on a banknote
UK coins resting on a banknote.Image: An image of coins laying on a bank note by HM Treasury, GOV.UK. Contains public sector information licensed under the Open Government Licence v3.0
  1. Measure the diameter with a ruler or, better, a calliper. Enter it in the coin diameter identifier to see every UK coin within a tolerance you choose.
  2. Weigh it on a kitchen or jewellery scale that reads to 0.01 g, then use the coin weight identifier.
  3. Still stuck? Try the UK coin identifier, which narrows by metal, shape and inscription.

A coin that is noticeably off the figures above may be worn, damaged, a foreign coin or a fake. A 12-sided £1 well under 8.75 g is worth a closer look: see how to spot a fake £1 coin.

Frequently asked questions

How big is a 1p coin in mm?
A 1p is 20.3 mm across and weighs 3.56 g. It is 1.65 mm thick if it is copper-plated steel (1992 onwards) and 1.52 mm if it is the older bronze coin. The size has not changed since 1971.
How big is a 2p coin in mm?
A 2p is 25.9 mm across, weighs 7.12 g and is 2.03 mm thick (1.85 mm for the pre-1992 bronze coin).
Which UK coin is the biggest?
Of the coins in circulation, the £2 is the widest at 28.4 mm and the heaviest at 12 g. The 50p (27.3 mm) and 2p (25.9 mm) come next. The smallest is the 5p at 18 mm.
Why is the 10p bigger than the 20p?
The 10p (24.5 mm) was sized to replace the two shilling coin in 1968, while the 20p (21.4 mm) arrived in 1982 as a smaller, seven-sided coin to fill the gap between the 10p and 50p. Coin size in the UK has never followed face value.
Are old 5p, 10p and 50p coins bigger?
Yes. The original 5p was 23.59 mm, the original 10p 28.5 mm and the original 50p 30 mm. All three were replaced by smaller coins between 1990 and 1997 and are no longer legal tender.
How can I identify a coin by its size?
Measure it with a ruler or calliper and enter the figure in our coin diameter identifier, or weigh it on a kitchen scale and use the coin weight identifier. Both match against every UK coin in the MyCoinage catalogue.

Further reading

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Reviewed by Connor Jones, Editor. Every MyCoinage guide is fact-checked against realised auction sales before publication: read our editorial policy.
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