It's difficult to generalize. If you are referring to molded case circuit breakers, then a 3 to 1 ratio between similar breakers should coordinate relatively well in the overload (thermal) range, but probably will not coordinate in the instantaneous range. This depends on the breaker characteristics and adjustability, but also on the available fault current. In general, you cannot assume molded case breakers will coordinate in the instantaneous ranges unless you evaluate the time current curves over the range of available fault current. If you absolutely must have complete coordination at low voltage, then fuses are the best option. Generally a 2 to 1 size ratio between similar current-limiting fuses should always coordinate. For a few types a 3 to 1 ratio is required. This is based on testing by the fuse manufacturers. Of course fuses have other drawbacks.