Overview

Decimal Day is the informal name given to 15 February 1971, the date on which the United Kingdom switched its currency to a purely decimal system. Before that date the currency was expressed in pounds, shillings and pence; after Decimal Day the pound was divided into 100 new pence (abbreviated "p"). The reform simplified arithmetic and everyday transactions and brought the UK into line with most other modern currencies.

Pre-decimal system and terminology

The earlier system is commonly referred to by the letters £sd (spoken L‑S‑D), derived from Latin names. It used three units: the pound (£), the shilling (s) and the pence (d). In that arrangement £1 equalled 20 shillings and one shilling equalled 12 pence, so £1 was equal to 240 pence. The older abbreviations and coin names remained familiar to many people for decades, and the historical terms are still used when discussing prices and antiques. The letters in the abbreviation are sometimes linked to the system of unit abbreviations.

Reasons for change and preparation

Decimalisation was motivated by the desire for simpler calculations, easier pricing and international compatibility. A dedicated body coordinated the reform and a public education campaign prepared households and businesses. During the late 1960s some decimal coins were introduced ahead of the main change so they could circulate alongside pre‑decimal coins; for example, the five‑pence and ten‑pence pieces matched the value and size of older coins that they replaced.

The changeover and practical effects

On Decimal Day the pound officially became equal to 100 new pence. Conversion required revised pricing, updated accounting systems and new coinage. For reference, 1 new penny equalled 2.4 old pence, and a new five‑pence coin corresponded in value to an old shilling. Many businesses displayed prices in both systems for a transitional period and retailers, banks and schools ran information programmes to help the public adapt.

Legacy and notable facts

Decimal Day is a milestone in British monetary history and a common reference point in discussions about currency reform. While the UK retained the pound sign and the name "pound sterling," the move reduced everyday computation and influenced later changes in coin sizes and denominations. The event is often cited as an example of a large, centrally organised administrative change that combined legislation, logistics and public communication.

  • Key conversion: £1 = 20s = 240d (old); £1 = 100p (new).
  • Decimalisation eased trade and accounting with many other nations.
  • Transitional measures included dual pricing and phased coin introductions.