RIRLift app icon RIRLift

Exercises

Chest fly: how to do it, what it works, and what to swap it for

Published October 17, 2026

A chest fly is a chest isolation exercise: you lie on a flat bench with a dumbbell in each hand and open your arms in a wide arc, then bring them back together over your chest. It trains the pecs, with the front delts helping, and it loads them hardest at the bottom, where your chest is stretched. It works when your elbow angle stays fixed for the whole set, so only your shoulders move and your elbows never press the weight.

Your last dumbbell chest fly set

How to do the dumbbell chest fly

The fly is hardest where your chest is longest, the part of the rep that presses barely load. It needs a light pair of dumbbells and a flat bench, so it slots in after your pressing on any chest day.

Steps

  1. Sit on the end of a flat bench with the dumbbells on your thighs, then lie back and press them up over your chest, palms facing each other.
  2. Plant your feet, pull your shoulder blades back into the bench and soften your elbows into a slight bend.
  3. Open your arms in a wide arc, taking about two seconds, until your upper arms reach bench level and you feel a strong stretch across your chest.
  4. Squeeze your chest to bring the dumbbells back up along the same arc, keeping the elbow bend you started with.
  5. Stop when the dumbbells are a hand's width apart, then start the next rep.

Cues

  • Hug a barrel
  • Elbow bend fixed
  • Stop at bench level

Common mistakes

  • Letting your elbows fold as the dumbbells come down: once they bend further, the fly becomes a press, so drop to a lighter pair.
  • Chasing depth below the bench: stop when your upper arms reach bench level and the stretch across your chest is strong.
  • Clanking the dumbbells together at the top: your chest goes slack there, so stop a hand's width apart.

Swap for: Dumbbell Floor Fly, Pec Deck Fly, High-to-Low Cable Fly

Muscles the dumbbell chest fly works

The chest fly trains the pectoralis major, mostly its middle fibers on a flat bench, with the front delts helping. Because your arms stay long, the load peaks at the bottom of the arc, where the chest is stretched, and fades to almost nothing at the top.

Sets, reps and reps in reserve for the dumbbell chest fly

GoalSets × repsRIRRest
Build muscle 3 × 12–20 2 90 s
This matches what the session builder prescribes for the dumbbell chest fly.
Last exercise of a chest day 2–3 × 12–20 0–1 60–90 s
Take the last set close to failure here, since no heavy pressing follows it.
Beginners 2–3 × 12–15 2–3 90 s
Stay further from failure for the first few weeks while you learn to hold the elbow angle.

Dumbbell chest fly variations

  • Incline Dumbbell Fly start position

    Incline Dumbbell Fly

    Pick this when your upper chest lags: set the bench to about 30 degrees and the arc lines up with the fibers under your collarbone.

    Build a session with it
  • Decline Dumbbell Fly start position

    Decline Dumbbell Fly

    Pick this when you want the lower part of your chest to take more of the work.

    Build a session with it
  • Dumbbell Floor Fly start position

    Dumbbell Floor Fly

    Pick this when you have dumbbells but no bench; the floor stops your arms at a good depth on every rep.

    Build a session with it
  • High-to-Low Cable Fly start position

    High-to-Low Cable Fly

    Pick this in a gym with a cable station when you want resistance that stays on near the top of the rep, where dumbbells go light.

    Build a session with it

Dumbbell chest fly alternatives

In the gym

  • Pec Deck Fly start position

    Pec Deck Fly

    Use the pec deck when you want to push a fly close to failure without balancing two dumbbells.

    Build a session with it
  • Flat Dumbbell Press start position

    Flat Dumbbell Press

    Press instead when you would rather move heavier weight; the dumbbells still sink deep enough to stretch your chest.

    Build a session with it

At home

  • Push-Up start position

    Push-Up

    Do push-ups when you have no weights at all, and raise your feet or slow the lowering once 20 reps come easily.

    Build a session with it
  • Single-Arm Band Chest Fly start position

    Single-Arm Band Chest Fly

    Anchor a band beside you when you want the fly motion with no dumbbells or bench.

    Build a session with it
  • TRX Chest Fly start position

    TRX Chest Fly

    Use a suspension trainer when you have one: walk your feet back to make each rep harder.

    Build a session with it

A different stretch

  • Dumbbell Chest Pullover start position

    Dumbbell Chest Pullover

    Reach one dumbbell overhead when you want to stretch your chest with the arms above your head instead of out to the sides.

    Build a session with it
  • Deep Push-Up start position

    Deep Push-Up

    Push up from handles or blocks when you want the bottom stretch of a fly in a bodyweight press.

    Build a session with it

Chest fly vs chest press

A press moves the weight with your shoulders and elbows together, so you can load it heavy and it is hardest near the bottom and middle. A fly locks the elbows, leaves the chest to do the work alone, and puts the hardest part of the rep at the deep stretch, with much lighter dumbbells.

You do not have to choose. Press first while you are fresh, then add two or three fly sets, and count both toward the 10–20 hard chest sets you do each week. The chest exercises with dumbbells page lays out presses and flies side by side.

How heavy should your chest fly be?

Lighter than you expect. Pick the pair you can lower to bench level for at least 12 reps without your elbows bending further, and finish each set with about two reps left. When you reach the top of the rep range on every set with that form, move up one pair next session.

Questions

What is a chest fly good for?

It loads your chest at long length, in the stretched part of the rep that presses barely touch, and it needs only light dumbbells. That makes it a good second exercise after a press to add chest sets without heavy weight.

Do chest flies grow your chest?

Yes, when the sets are hard. Take each set to within 0 to 2 reps of failure and count the flies with your presses toward 10 to 20 hard chest sets a week.

Is a chest fly harder than a bench press?

Per pound, yes: your arms stay long, so a light pair of dumbbells feels heavy at the bottom. You will use far less weight on a fly than on any press, and that is expected.

How do you do a chest fly at home?

Lie on the floor with a pair of dumbbells and do a floor fly, letting your upper arms touch the floor at the bottom of each rep. With no dumbbells, anchor a band beside you for a band fly, or do push-ups.

What can I do instead of a chest fly?

A pec deck or cable fly keeps the same arm motion. A dumbbell press or push-up trains the same muscles with heavier load, and a dumbbell pullover stretches the chest from overhead.

Do I really need chest flies?

No. Presses and push-ups can build your chest on their own. Flies are worth adding when you want more chest sets without more heavy pressing, or when your chest feels like it does little during your presses.

How many sets and reps of chest fly should I do?

Start with 3 sets of 12 to 20 reps, stopping each set with about two reps left and resting 90 seconds between sets.