It is really important that you keep your Labrador’s weight appropriate for his height and build, rather than following guidelines on food packets or in books too closely.
The best way to tell is by eye and touch.
Have a look at your dog and compare him with this picture of a healthy Labrador.
Look at your dog from the side. Does his belly slope upwards towards his groin, or is it a level line from his front legs to his back, or even worse is it sagging down between his legs?
Your Labrador should have an upward sloping line from the base of his chest, towards his back legs.
Now look at the dog from above. Can you see a ‘waist’ just in front of his hips? You should be able to! Your dog should not be the same width all the way down his body.
Look at your dog from the side again. Can you see any ribs? You should not be able to see a lab’s ribs whilst he is standing still though you may well be able to see the last one or two when he is eating, drinking or bending and twisting.
Run you hands along his rib cages firmly. Can you feel his ribs? Ideally you should be able to just feel, but not see, your dog’s ribs. If you can see ribs when he is standing still he is too thin. If you cannot feel his ribs at all with your hands he is too fat!