Hello friends, please use a flexible fabric tape measure to find the biggest width of your dog, take care to measure their neck and belly. We really recommend that you also add two fingers (2cms) to fit inside the tape when measuring - this will ensure that the product is not too tight.
If your dogs measurements are are towards the upper limit of a size bracket, we suggest sizing up. The length of the product is to aid dog breeds which have deep chests, this may pull the harness forward so the buckles sit underneath the dogs legs. For most breeds, this should not be an issue.