When one brake caliper fails, a common question is whether you must replace both on that axle - like you would with pads or rotors. Unlike those, calipers are not an automatic pair replacement, but there are times it makes sense. Here is how to decide.
Calipers are not automatically paired
Pads and rotors are always replaced as an axle set so both sides brake evenly - but a caliper is a durable component; see do you replace calipers with pads. If one caliper fails and the other is healthy, you can replace just the failed one. There is no rule that calipers must be swapped in pairs.
When replacing both is wise
Consider doing both if the vehicle is high-mileage and the other caliper is likely near failure too - especially in the rust belt where salt attacks both sides equally; see calipers at high mileage. Replacing both at once saves a second labor charge soon after, and guarantees even, matched braking - a stronger new caliper on one side vs a tired one can cause a slight pull.
When one is fine
On a newer, low-mileage car where one caliper failed from a specific cause (a stone-damaged boot, say) and the other is clearly healthy, replacing just the bad one is perfectly acceptable and saves money. Inspect the good side - free-moving slides, intact boot, no leak, even pad wear - to confirm.
Either way, do pads and rotors as a set
Whatever you decide on calipers, always replace pads (and rotors if due) as an axle set, and fix the failed caliper before fitting new friction. Quality pads and fresh hardware with a sound caliper on each side gives even, safe braking.