Body weight directly affects the energy cost of running. Using Daniels’ rule of thumb (time scales roughly with weight^0.67), see what a weight change would do to your result.
Frequently Asked Questions
Does losing weight always make me faster?
Not necessarily. Losing fat usually helps, but losing muscle, under-fuelling and poor recovery cancel the benefit.
What is the basis of the rule?
Daniels notes roughly a 0.6–0.7% time change per 1% of body weight; this tool models that relationship.
What is a healthy weight?
Use BMI, body-fat percentage and medical advice — never race time alone as the target.
Gear runners ask about
GPS running watch
Pace, laps and alerts on your wrist
Chest strap heart-rate monitor
More reliable than wrist-based HR
Race day running shoes
Lightweight shoes for tempo and race pace
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