What size are the UK’s armed forces?

The strength of the UK’s armed forces has frequently been in the spotlight since the outbreak of war in Europe three years ago. We’ve seen claims that the number of troops is at a “record low” and decreasing, that the Army is at its smallest size since the Napoleonic Wars or that it can fit into Wembley Stadium, and reports of concern at the forces’ fighting strength. We’ve also seen senior Conservative politicians challenged over the numbers and a misleading Labour party graph about planned cuts to the army, and there’s been debate over the potential need for mass mobilisation. 

There are multiple ways to quantify the strength of the armed forces. Some see defence expenditure as an indication of strength, while others think weapons, firepower, equipment or personnel are better indicators. We’ve written elsewhere about some of these topics—particularly defence spending—but this explainer focuses on how personnel are counted across the armed forces and how the size of the forces compares historically and internationally. 

Measuring the number of personnel can be complicated, given there are three separate forces—the Army, the Royal Navy (which also includes the Royal Marines) and the Royal Air Force (RAF). There are also multiple types of personnel, such as the UK Regulars, Gurkhas, mobilised reservists and Nursing Service personnel, and excluding or including different groups can paint different pictures about the size of the forces. 

This explainer is one of a series Full Fact has published exploring a range of key political topics. We’ll be updating these articles on a regular basis—this article was last updated on 4 March 2025 and the information in it is correct as of then. 

How is the number of personnel measured?

Figures for the number of personnel differ depending on which definition is used. 

‘UK Forces’ is a term used by the Ministry of Defence (MOD) to count the number of total full-time trained and untrained UK service personnel and is considered by the House of Commons Library to be the most comprehensive of the measures. 

It counts members of all three forces, including: UK Regular Forces, Gurkhas, Military Provost Guard Service, Locally Engaged Personnel, Volunteer Reserve, Serving Regular Reserve, Sponsored Reserve and elements of the Full-Time Reserve Service.

By this measure, the strength of the UK Forces was 180,779 personnel as of 1 January 2025, according to the latest figures. This is a decrease of 1.3% since 1 January 2024. 

Broken down by force type, there were 37,601 personnel in the Royal Navy (including the Royal Marines), 108,413 in the Army and 34,765 in the RAF.

The strength of the UK Forces can also be broken down by personnel type. The 180,779 personnel across all three branches of the armed forces includes 136,117 members of the UK Regular Forces, 4,127 Gurkhas, 31,967 members of the Volunteer Reserve and 8,568 other personnel.  

It’s also possible to break down each of the three armed forces branches by the number of UK Regular Forces, Volunteer Reserves and Other Personnel. (Only the Army has Gurkhas—Nepalese soldiers who are employed in the British Army under the terms of the 1947 Tri-Partite Agreement.)

The term ‘UK Regular Forces’ (or UK Regulars) is a measure of the UK armed forces’ permanent personnel, including Nursing Services staff. Of the 136,117 UK Regular Forces (trained and untrained) personnel as of 1 January 2025, 31,906 were in the Royal Navy or Royal Marines, 73,847 in the Army and 30,364 in the RAF. 

‘Full-Time Trained Strength’ measures trained personnel from the UK Regular Forces, Gurkhas and the Full-Time Reserve Service. 

Until 2016, the Army’s definition of Trained Strength only included troops that had passed Phase Two, or specialist, training. But since 2016, the Army has included personnel who have passed Phase One, or basic skills training, in its definition of ‘trained’. 

Royal Navy and RAF figures for trained personnel only include those who have passed Phase Two training. 

The total ‘Full-time Trained Strength’ of the armed forces is 130,930. 

Meanwhile the Army uses an additional term, ‘Full-Time Trade Trained Strength’, to count personnel who have completed both phases of their training. 

The MOD also produces a figure which combines Full-Time Trained Strength for the Royal Navy and RAF (ie, those who have completed both phases of training) with the Full-Time Trade Trained Strength of the Army. In this explainer, we will refer to this combined figure as personnel who are ‘fully trained’. 

This is the definition used in personnel targets. 

There are 127,036 full-time fully trained personnel in the forces, including 71,151 in the Army, 28,085 in the Royal Navy/Marines and 27,800 in the RAF.

How has the size of the armed forces changed over time? 

In the year to January 2025, the strength of UK Forces decreased by 2,353 (1.3%), while the strength of fully trained forces decreased by 3,622 (2.8%). 

As the Army’s definition of “trained” changed in 2016, for longer-term historical comparisons it’s better to look at the data for full-time trade trained strength since 2016 instead. Between 2000 and 2024,, the number of fully trained personnel across all forces decreased by by 32%, with the Army seeing a fall of about 28%, the Royal Navy/Marines 26% and the RAF 45%. 

For an even longer historical comparison, the best data we’ve been able to find was released by the MOD in response to a Freedom of Information request in 2017.

The figures are for UK Regular Forces, and come with a health warning—while there is some data as far back as 1700, the government says “figures prior to 1900 have not been sourced, and therefore their reliability is unclear”. 

The data since 1900 shows the size of the UK’s Regular Forces is currently at its lowest in that period.

The two spikes in the graph above show the First World War and the Second World War. In 1916, conscription was introduced for all single men aged between 18 and 41 (with some exemptions), which dramatically increased the number of personnel in the armed forces. National Service was introduced in 1939, at the start of the Second World War, which made it compulsory for many men aged between 18 and 41 to join the armed forces.   

National Service remained in place following the Second World War, until 1960, though within this period it applied only to physically fit males between the ages of 17 and 21. They had to serve in one of the forces for 18 months. 

It’s also worth noting the RAF was established in 1918, so data from 1900-1917 includes only the Army and Royal Navy. 

The reliability of the data going back to 1700 is unclear, and some years are missing data.

A claim we’ve heard multiple times before is that the Army is currently at its smallest size since the Napoleonic era, the wars of which took place between 1792 and 1815.

This appears to be broadly correct, though there are caveats around the data.

The historic data released by the government shows, at the start of the Napoleonic wars, the UK Army Regular Forces’ strength was around 17,000. This increased during the next couple of decades, before reaching 237,000 in 1814.

These figures suggest that the size of the UK Army Regular Forces, which was  67,107 at the beginning of 2025, was last smaller than that in 1803. 

There are a number of caveats to this. The UK Army Regular Forces measure doesn’t necessarily represent the full strength of the Army—it doesn’t, for example, include the reserves or Ghurkas. And Army-specific data is missing from the MOD figures between 1861 to 1900, though given there were 236,000 in the Army in 1860 and 302,000 in 1900, it seems unlikely numbers would have dipped below the current figures over those 40 years, especially given the emergence of the British empire during the 19th century. 

Overall then, it is not unreasonable to say that the British Army is now comparable in terms of personnel to the Napoleonic era, despite the caveats listed above.

In March 2025 we saw a claim from Russian state media that “you could fit the whole British army into Wembley Stadium”. Whether this is true depends on whether or not you count the Army Reserves.

Wembley Stadium’s capacity is approximately 90,000. While the number of full time trained Army personnel would be able to fit into Wembley with room to spare, there are also 25,742 Volunteer Reserves in the Army. The Army’s total personnel — including Regular Forces, Gurkhas, Volunteer Reserves and Other Personnel — is 108,413, which is above Wembley’s capacity. 

How does the size of the UK’s armed forces compare internationally?

Comparing the size and strength of armed forces internationally can be tricky. Military strength can be judged in multiple ways, such as firepower, the number of vessels, aircraft, submarines or tanks a nation has, the number of atomic weapons held, or budget. So the number of personnel serving may not reflect the overall strength of a country’s armed forces.

And as already noted even within the UK context, there are multiple ways manpower can be counted (for example, active personnel, all reserves or personnel per head of the population). 

The International Institute for Strategic Studies looked at relative numbers of armed forces personnel in 2020, counting full-time “active duty military personnel” including “conscripts and long-term assignments from the Reserves” and paramilitary forces. By that measure it found India had the most personnel, at 3.07 million, followed by China with 2.54 million, North Korea with 1.5 million, Russia with 1.45 million and the USA with 1.4 million. The UK was ranked 41st. 

Around 85 countries have a form of obligatory military service or training, including Russia and North Korea.

Data from 2018 gives an idea of the number of active duty military personnel countries have as a share of population. This shows 0.2% of the UK’s population were military service personnel that year—the same proportion as in India and China. The nations with the highest proportion of their population serving in the armed forces were Eritrea (5.8%), North Korea (5.7%) and Israel (2.1%). These three countries have mandatory national service.

Image courtesy of UK MoD