For adults, chest compressions during CPR should be at least 2 inches (5 centimeters) deep but no more than 2.4 inches (6 centimeters). For children, the target is about one-third to one-half the depth of the chest. These numbers come from American Heart Association and Mayo Clinic guidelines, and hitting the right range is one of the most important factors in whether CPR actually works.
Adult Compression Depth
The target zone for adult CPR is narrow: at least 2 inches, no more than 2.4 inches. That’s roughly the width of a credit card stacked on its edge. Compressing to this depth generates enough pressure to squeeze the heart between the breastbone and spine, pushing blood out to the brain and vital organs. Too shallow and you’re not moving enough blood. Too deep and you increase the risk of internal injury without improving outcomes.
Reaching this depth takes real physical effort. The Mayo Clinic recommends using your entire body weight rather than just arm strength. You should position yourself directly over the person’s chest with your arms straight and shoulders stacked above your hands. This lets gravity do much of the work, which matters because effective CPR is exhausting and rescuers tend to compress more shallowly as they fatigue.
Depth Guidelines for Children and Infants
Children and infants have smaller, more flexible rib cages, so CPR depth is measured as a proportion of chest size rather than a fixed number. For children ages 1 to 8, compressions should reach about one-third to one-half the depth of the chest. In practice, that works out to roughly 2 inches for most children, though smaller kids will need less.
For infants under 1 year old, the same one-third proportion applies, but you use two fingers or two thumbs instead of your full hands. The chest is so small that even modest pressure reaches the target depth. The proportional rule exists because a fixed depth that’s appropriate for a large child could cause serious harm to a newborn.
Why Full Chest Recoil Matters as Much as Depth
Pushing deep enough is only half the equation. After each compression, you need to let the chest spring all the way back to its resting position before pushing again. When the chest recoils fully, it creates a vacuum effect inside the rib cage that draws blood back into the heart. Without that refill, the next compression has less blood to push out, and circulation drops even if your depth is perfect.
A common mistake is leaning on the chest between compressions. This keeps the ribcage partially compressed, reduces the vacuum effect, and limits how much blood returns to the heart. Think of it as a pump: you need to let the handle come all the way up before you push it down again, or you’re only moving a fraction of what you could.
Rib Fractures Are Common and Expected
One reason people hesitate to push hard enough is fear of breaking ribs. That fear isn’t unfounded, but it shouldn’t stop you. A large autopsy study from Ljubljana analyzed over 2,100 cardiac arrest patients and found that rib fractures occurred in 77% of men and 85% of women who received CPR. Sternum (breastbone) fractures showed up in 59% of men and 79% of women. The average person had about 11 skeletal injuries from compressions.
Those numbers are much higher than most people assume. Previous estimates suggested only about one-third of patients sustained rib fractures, but detailed post-mortem analysis revealed the actual rate is far higher. The injuries increase with age as bones become more brittle. Despite these numbers, severe accompanying injuries occurred in fewer than 2% of cases. Broken ribs heal. A person in cardiac arrest who doesn’t receive CPR won’t get that chance.
Adjustments for Larger or Older Patients
The standard 2-to-2.4-inch range works well for most adults, but research suggests it may not be ideal for everyone. A study using chest CT scans found that the standard compression depth maintained effective heart compression and blood flow in the general population, but was less effective for obese and elderly individuals. In these groups, compressing to one-quarter to one-third of the external chest diameter produced better results.
For a larger person with a deeper chest, 2 inches of compression may not reach the heart effectively. For a very elderly person with a thinner, more fragile chest, 2.4 inches might be proportionally excessive. In an emergency, you won’t have time to calculate ratios, but knowing that bigger chests may need firmer effort and frail chests need a lighter touch can help you adjust instinctively.
How to Judge Depth Without a Device
Professional rescuers sometimes use electronic feedback devices that measure compression depth in real time, but most bystanders won’t have one. Without a gadget, you’re relying on feel and body mechanics. Two inches is roughly the distance from the tip of your index finger to the first knuckle crease. Visualizing that distance before you start can help calibrate your effort.
The most reliable approach is positioning. Kneel beside the person, place the heel of one hand on the center of the chest (on the lower half of the breastbone), stack your other hand on top, and lock your elbows straight. With your shoulders directly above your hands, push straight down using your upper body weight. If you’re compressing from an angle or bending your elbows, much of your force is wasted and you’ll consistently fall short of the target depth.
Push hard, push fast (aim for 100 to 120 compressions per minute, roughly the tempo of “Stayin’ Alive”), and let the chest come all the way back up between each push. If you’re not a little winded after 30 seconds, you’re probably not pushing hard enough.