Consistency is the goal
A tape estimate is not a laboratory truth, but repeat measurements can show direction of change.
Measure the same way
Place the tape at the same heart-girth location, with the horse square and relaxed.
Formulas are approximations
Breed, age and body shape influence accuracy. Minis, drafts and growing horses may need different methods.
Medication requires better accuracy
For important dosing, use a veterinary scale when possible or discuss the safest estimate with your veterinarian.
Pair with body condition
Weight alone cannot tell you whether the horse is too fat, too thin or under-muscled.