Correct chest compressions for adults require pushing hard and fast on the center of the chest to a depth of 5 to 6 centimeters (2 to 2.5 inches) at a rate of 100 to 120 compressions per minute. These two numbers, depth and rate, are the most critical factors in keeping blood flowing to the brain and heart during cardiac arrest.
Rate and Depth
The 2025 American Heart Association guidelines confirm the target rate of 100 to 120 compressions per minute. Studies of over 13,700 patients found improved survival to hospital discharge when compressions landed in the 100 to 119 per minute range, compared with rates that were slower or faster. Going above 120 per minute tends to reduce compression depth, which cancels out the benefit of speed.
Each compression should push the chest down 5 to 6 centimeters, or roughly 2 to 2.5 inches. Shallower compressions don’t generate enough pressure to move blood through the heart. Deeper compressions raise the risk of injury without improving outcomes. Using your body weight rather than just arm strength is the easiest way to consistently hit that depth.
Where to Place Your Hands
Place the heel of one hand on the breastbone, just below the nipple line. Put the heel of your other hand directly on top of the first, then interlock your fingers. Keep your arms straight with your shoulders positioned directly above your hands so that each compression travels straight down. Pressing at an angle wastes force and shifts the compression away from the heart.
Why Full Chest Recoil Matters
Between each compression, let the chest come all the way back up to its normal position. This isn’t a rest period. It’s an active part of the cycle. When the chest springs back, it creates a brief negative pressure inside the chest cavity that pulls blood back into the heart from the veins, essentially refilling the pump before the next squeeze.
Leaning on the chest even slightly between compressions blocks this refilling mechanism. Animal studies found that leaning by as little as 10 to 20 percent of compression depth raised pressure in the veins, reduced blood flow to the heart muscle, and dropped overall cardiac output. In practice, this means lifting your weight completely off the chest between pushes while keeping your hands in contact with the breastbone.
Compressions With or Without Breaths
The standard ratio is 30 compressions followed by 2 rescue breaths, repeated in cycles. This applies whether one or two rescuers are performing CPR before emergency medical services arrive.
If you’re untrained or uncomfortable giving rescue breaths, hands-only CPR (continuous compressions with no breaths) is not just acceptable but may be more effective for bystanders. A meta-analysis pooling data from over 3,700 patients found that compression-only CPR had a higher survival rate at hospital discharge: 11.5 percent compared with 9.4 percent for standard CPR with breaths. The likely reason is simple. Pausing compressions to deliver breaths interrupts blood flow, and untrained rescuers tend to pause too long. Keeping compressions going without interruption maintains more consistent circulation.
There are exceptions. Rescue breaths remain important when the cardiac arrest has a non-cardiac cause (like drowning or choking), in children, and when more than four minutes have passed since the arrest began. In these situations, oxygen delivery becomes a limiting factor.
Surface and Body Position
The person should be lying face-up on a firm, flat surface. A soft mattress or couch absorbs compression force, meaning less of your effort actually reaches the heart. If someone collapses on a bed, moving them to the floor is preferred as long as it doesn’t delay the start of compressions. In hospitals, staff use backboards or activate a “CPR mode” on the bed to firm up the mattress.
Switching Rescuers Every Two Minutes
Compression quality drops faster than most people realize. The AHA recommends switching with another rescuer at least every two minutes, or sooner if you feel fatigued. Even rescuers who believe their compressions are still adequate tend to lose depth and rate well before they feel tired. If two people are available, trading off every two minutes keeps compression quality consistent until paramedics arrive.
Rib Fractures During CPR
Cracked ribs are common during correctly performed CPR, not a sign that something went wrong. Rib fractures occur in over 70 percent of CPR cases, with an average of about 7.6 broken ribs per person. This statistic can feel alarming, but broken ribs heal. A heart that stops beating without intervention does not. If you feel or hear a crack while performing compressions, continue at the same depth and rate.
Quick Reference
- Compression rate: 100 to 120 per minute
- Compression depth: 5 to 6 cm (2 to 2.5 inches)
- Hand placement: heel of hand on center of breastbone, just below the nipple line
- Ratio: 30 compressions to 2 breaths (or continuous compressions if untrained)
- Recoil: allow full chest rise between each compression
- Surface: firm and flat, face-up
- Rescuer swap: every 2 minutes