Estimate open water swim distance.
Hydration needs for Open Water Swim Distance start from body weight and add allowances for prolonged activity and hot conditions, where sweat losses climb. Fluid needs track body size and sweat loss, so a fixed daily target fits nobody precisely.
Open Water Swim Distance
Water = 33 mL x weight + activity allowance + heat allowance
These figures are population-average estimates for training and recreational planning only and are not medical advice. Individual responses vary widely. Consult a qualified health professional before starting or significantly changing an exercise programme, particularly if you have any medical condition. Official dimensions, rules and timings should be confirmed against the governing body for your sport.
Water = 33 mL x weight + activity allowance + heat allowance Hydration needs for Open Water Swim Distance start from body weight and add allowances for prolonged activity and hot conditions, where sweat losses climb.
Fluid needs track body size and sweat loss, so a fixed daily target fits nobody precisely.
This calculator takes 3 inputs: Body weight, Activity, Temperature. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.