Hydration Pack Calculator — What Size Pack Do You Need
Calculate the hydration pack capacity you need for long runs and ultras.
How We Calculate This
Hydration Capacity Planning
Your fluid needs depend on duration, temperature and aid station access:
Fluid Need = Duration (hrs) x Intake Rate (ml/hr)
Typical rates: 400 ml/hr (cool), 600 ml/hr (warm), 800 ml/hr (hot).
If aid stations are available, you can carry less and refill along the way.
Frequently Asked Questions
Related Calculators
Shoe Mileage Calculator
Track shoe mileage and estimate when to replace your running shoes.
Shoe Size Calculator
Convert running shoe sizes between UK, US and EU systems.
Shoe Rotation Calculator
Plan your shoe rotation schedule to extend shoe life.
Clothing Layer Calculator
Calculate what to wear based on temperature and conditions.
Reflective Gear Calculator
Check if you need reflective gear based on your running time.
Last updated: February 2026
All calculations are estimates. Always consult a coach or medical professional for personalised training advice.