It is usually better to replace your calipers in pairs. If just one caliper is not working, you do not have to replace the calipers for all four wheels. However, you should replace the right and the left one in either the front or the back.
There are some situations where this is not necessary. If the unaffected caliper is new anyway, it might not be worth the expense to replace both calipers. However, if they have both been on the car for a long time, it’s likely that both have a fair amount of wear and tear, even if one of them is still working well.
The other caliper will likely need to be replaced soon anyway. Having one brand new caliper and one old one could lead to problems in driving performance.
