How Fast and How Deep Should Chest Compressions Be?

If someone has collapsed and is not breathing normally, chest compressions are what keeps blood moving to their brain until the ambulance arrives. Push at a rate of 100 to 120 compressions a minute, which is roughly two every second, and press down hard to a depth of about 5 to 6cm on an adult chest before letting it come back up¹. If you are trained and willing, give two rescue breaths after every 30 compressions; if you are not, keep the compressions going without stopping for breaths².

The pace and the depth matter more than anything else you do. Every minute that passes without CPR and a defibrillator, a person's chance of survival falls by about 10%⁴. When early CPR and a defibrillator are used within the first 3 to 5 minutes, survival rates can increase up to 70%⁶. That is why the advice is to start compressions straight away and keep them going, rather than waiting for someone more qualified to arrive.

This page sets out the rate and depth for adults, children and babies, how the 30:2 pattern works, what to do if you are on your own or tire, and how a defibrillator fits around the compressions. It is general first aid guidance, not a substitute for a training course, and it applies across the UK.

Push 100 to 120 times a minute until the ambulance arrives

The target rate for adult chest compressions is 100 to 120 per minute¹. Several ambulance services put it more simply: about two compressions every second⁸. The British Heart Foundation describes pressing down smoothly and firmly at a rate of 2 per second⁹. The Resuscitation Council UK says to push down hard and then release twice per second, and not to stop¹⁰.

The depth is just as important as the speed. Press down hard, to a depth of about 5 to 6cm, then release the pressure and allow the chest to come back to its original position². North East Ambulance Service puts it as pressing down hard and fast by 5 to 6cm on the chest¹. Use your body weight rather than just your arms, and lean directly over the person's chest so you are pressing vertically⁷.

Two things commonly go wrong. The first is pressing too shallowly because you are worried about hurting the person. The second is leaning on the chest between compressions so it never fully comes back up. Keeping your hands on the chest but releasing the compression fully lets the chest refill with blood between pushes¹¹.

If you have had no training, the ambulance services' hands-only approach is the one to follow: push hard and fast in the centre of the chest and keep going⁴. You do not need to count to a particular total; you need to keep the rate and depth steady.

30 compressions, then 2 rescue breaths

If you are trained to give rescue breaths, the pattern is 30 compressions followed by 2 rescue breaths, then repeat². The Resuscitation Council UK's 2025 adult basic life support guidelines say the same: alternate 30 chest compressions with 2 rescue breaths if you have been trained to provide them¹². Keep alternating 30 compressions with two breaths, known as 30:2, until help takes over².

A few practical points make the breaths work. Stick to two attempts to get the breaths in; if one or both do not work, return to chest compressions². Do not spend a long time trying to get a breath in, because every second off the chest is a second without circulation. If you are giving breaths to a child, the guidance is to blow gently and steadily for up to one second until the chest rises¹³.

Hands-only CPR: keep the same rate without stopping

Hands-only CPR is continuous chest compressions with no rescue breaths. It is the right choice if you are not trained, if you are unwilling to give mouth-to-mouth, or if you simply cannot face it in the moment. The rate is the same 100 to 120 times a minute¹¹. Repeat the compressions at that rate until an ambulance arrives, you become exhausted, or the person starts to show signs of regaining consciousness, such as coughing, opening their eyes, speaking or breathing¹¹.

The technique is straightforward. Keeping your hands on their chest, release the compression and allow the chest to return to its original position¹¹. Do not stop between compressions. The London Ambulance Service's summary of the steps is to keep going at a rate of 100 to 120 per minute¹⁵.

Hands-only CPR is not a lesser option. It is what the NHS advises if you are unable or unwilling to provide rescue breaths, and it keeps blood moving². The main thing is that you start, and that you keep the pace steady. If you later feel able to give breaths and you have been trained, you can switch to 30:2.

For a fuller walk-through of the sequence, from checking for danger to placing your hands, see how to do CPR: hands-only steps for adults. If you are deciding between the two approaches, rescue breaths or hands-only CPR sets out the trade-offs.

Child CPR uses the same 100 to 120 rate

The rate does not change for children. Give 30 compressions at a rate of 100 to 120 per minute, then two rescue breaths if you are trained¹⁶. The Resuscitation Council UK confirms that for children and infants you still compress approximately one third of the chest depth, at the same rate of 100 to 120 compressions per minute¹⁷. The difference is the depth and the technique, not the speed.

For a child aged one and over, the guidance is to give two rescue breaths after 30 chest compressions if you are trained, repeating 30 compressions followed by two breaths¹⁶. Some guidance for children starts with five initial rescue breaths before the 30:2 cycle, each full breath taking about one second¹³. For a baby under one, give 30 compressions at 100 to 120 per minute, then two rescue breaths if trained¹⁸.

There is one point where the official guidance is not fully settled. NHS inform's baby CPR page says to give two rescue breaths after 30 chest compressions if trained¹⁸, while other official guidance for babies describes five initial rescue breaths and then 30 compressions followed by two breaths¹⁹. Both agree on the rate and the 30:2 cycle; they differ on whether the first five breaths come before the cycle. If you are trained, follow the sequence you were taught. For a full walk-through, see how to do CPR on a child and how to do CPR on a baby under one.

Keeping the pace steady until help takes over

The hardest part of CPR is not starting; it is keeping the rate and depth steady for as long as it takes. Compressions tire you quickly, and tired compressions get shallower and slower. The answer is to share the work. If there are other people around, change who is giving the chest compressions every 1 to 2 minutes, with little disruption to the compressions⁷. The Resuscitation Council UK's guidance is the same: swap every one to two minutes if there is a helper, but try to minimise interruptions to chest compressions².

A changeover should take seconds, not a pause for discussion. The new rescuer kneels ready, the current rescuer counts the last few compressions aloud, and they swap on a count so the chest is not left still. If you are alone, keep going until emergency help arrives and takes over, the person starts breathing normally, you are too exhausted to continue, or a defibrillator tells you to stop while it analyses the heart rhythm³.

A defibrillator, if one is brought, works alongside you rather than replacing you. Keep doing compressions while the pads go on, then stop when the machine tells you to stand clear while it analyses the rhythm. After a shock, it will prompt you to start compressions again. Keep alternating 30 compressions with two breaths (30:2) until emergency help arrives and takes over, the person starts breathing normally, you are too exhausted to continue, or a defibrillator tells you to stop while it analyses the heart rhythm²⁰. In practice, you follow the voice prompts and keep pushing in between.

If the person is pulled from water, the advice differs slightly: if they are not breathing, they need five rescue breaths and then CPR, 30 chest compressions followed by two rescue breaths, continued until help arrives²¹. For more on that situation, see what to do after someone nearly drowns.

Where to learn and practise

Reading the rate and depth is a start, but CPR is a physical skill and practising on a manikin makes a real difference. Ambulance services across the UK run free community training, and the Resuscitation Council UK's public resources include a free online course. If you want to find a course near you, see first aid courses: types, length and where to find one, and for free online options, learning CPR free online.

The same rate and depth apply wherever you are in the UK. If you have a defibrillator at home, club or village hall, defibrillators (AEDs): what they do and how to use one explains how it fits with compressions, and public access defibrillators: finding the nearest one helps you locate one in an emergency.