For adults, chest compressions should be at least 2 inches (5 centimeters) deep. For children and infants, the target is about one-third the depth of the chest. These numbers come from the American Heart Association and remain the current international standard through 2025.
Getting the depth right matters more than most people realize. Too shallow, and the heart doesn’t get enough squeeze to push blood to the brain. Too deep, and the risk of rib fractures and internal injuries climbs. Here’s what you need to know to do it correctly.
Recommended Depth by Age
The guidelines break down by three age groups:
- Adults and adolescents: At least 2 inches (5 cm), but no more than 2.4 inches (6 cm).
- Children (ages 1 to 8): About one-third to one-half the depth of the chest, roughly 2 inches for most children.
- Infants (under 1 year): About one-third the front-to-back dimension of the chest, roughly 1.5 inches.
These targets haven’t changed in the most recent review cycle. The 2025 International Liaison Committee on Resuscitation (ILCOR) explicitly chose not to update its guidance on compression depth, meaning the existing recommendations remain in effect.
Why Depth Matters So Much
When you press down on the breastbone, you’re physically squeezing the heart between the sternum and the spine. This direct compression forces blood out of the heart and into the arteries, creating a temporary version of a heartbeat. Without enough depth, the heart doesn’t deform enough to generate meaningful blood flow. The brain and heart muscle begin to starve of oxygen within minutes.
Depth also drives coronary perfusion pressure, which is the force that pushes blood into the heart’s own blood vessels. Without adequate coronary perfusion, even a heart that could potentially restart won’t have the oxygen supply it needs to recover a normal rhythm. Every millimeter of compression depth translates to real differences in whether blood reaches the organs that matter most.
The Sweet Spot for Survival
A large study of out-of-hospital cardiac arrests, published in Circulation, found that peak survival occurred at a compression depth of about 45.6 mm (roughly 1.8 inches), with the highest survival rates falling between 40.3 and 55.3 mm (about 1.6 to 2.2 inches). This is slightly shallower than what the guidelines recommend as a minimum, which has prompted some debate among resuscitation scientists.
The practical takeaway: aiming for the recommended 2 inches puts you solidly within the survival sweet spot. Going significantly deeper than 2.4 inches (6 cm) starts to increase the risk of injury without improving outcomes. The guidelines set the floor at 2 inches because most bystanders tend to compress too shallowly rather than too deeply, so the emphasis on “at least” 2 inches is designed to push people past the most common mistake.
Depth and Rate Are Connected
Compression depth doesn’t exist in isolation. The recommended rate is 100 to 120 compressions per minute, and there’s an important tradeoff: as rate increases, depth tends to decrease. In one large dataset, 53% of cases where rescuers compressed faster than 120 per minute also had compressions shallower than 38 mm, which is well below the effective range. Pushing too fast often means you’re not pushing deep enough.
The rhythm that works best is steady and deliberate. Think of the beat of the Bee Gees’ “Stayin’ Alive,” which hits roughly 100 beats per minute. At that tempo, you can focus on pressing hard enough with each compression rather than racing through shallow ones.
Let the Chest Fully Recoil
After each compression, you need to let the chest come all the way back up to its normal position before pressing down again. This recoil phase is when the heart fills with blood. If you lean on the chest between compressions, even slightly, you raise the pressure inside the chest cavity and reduce blood flow to both the brain and the heart.
Studies using real-time monitoring have found that incomplete chest recoil happens 12 to 44% of the time, usually because the rescuer is leaning forward over the patient. It’s one of the most common and least recognized CPR errors. The fix is simple: lift your weight fully off the chest between compressions while keeping your hands in contact with the breastbone.
Correct Hand Placement
For adults, place the heel of one hand on the center of the breastbone, just below the nipple line. Place your other hand directly on top of the first, interlocking your fingers. Keep your arms straight and your shoulders directly above your hands so your body weight does the work, not your arm muscles. Compressing from this position helps you reach the correct depth without exhausting yourself quickly.
For children aged 1 to 8, you can often use just one hand on the breastbone in the same position, keeping the other hand on the child’s forehead to maintain an open airway. For infants, two fingers placed just below the nipple line on the breastbone are enough.
Hand placement affects more than just comfort. If your hands drift too low toward the bottom of the breastbone, compressions can push on the area near the aortic valve, which can actually obstruct blood flow out of the heart. Staying centered on the lower half of the breastbone, just below the nipple line, avoids this problem.
Rib Fractures and Injury Risk
Broken ribs are common during CPR, especially in older adults, and it’s normal to feel or hear a crack during compressions. This doesn’t mean you should stop or lighten up. The alternative to broken ribs is death from cardiac arrest, and the fractures heal. That said, deeper compressions do carry higher injury rates. Compressions in the 5 to 6 cm range, which is the upper end of the guidelines, are associated with more thoracic injuries than shallower ones.
Interestingly, rib fractures themselves can reduce CPR effectiveness. In animal studies, subjects with fewer fractures had better chest recoil, slightly larger chest dimensions, and significantly better coronary perfusion. This creates a difficult balance: you need enough depth to generate blood flow, but excessive depth causes injuries that compromise the chest’s ability to recoil. Staying within the 2 to 2.4 inch window gives you the best chance of threading that needle.
What Makes Compressions Effective
Putting it all together, effective chest compressions have five components that work as a package:
- Depth: At least 2 inches for adults, one-third chest depth for children and infants.
- Rate: 100 to 120 per minute.
- Full recoil: Let the chest return completely between compressions.
- Minimal interruptions: Pauses in compressions should be as brief and infrequent as possible.
- Correct placement: Heel of the hand on the lower half of the breastbone, below the nipple line.
Performing well on all five simultaneously is harder than it sounds, particularly as fatigue sets in. Compression quality degrades noticeably after about two minutes, which is why switching rescuers every two minutes is standard practice when more than one person is available. If you’re alone, focus on maintaining depth and rate for as long as you can until help arrives.