Electrolyte Calculator | Optimise Hydration, Sodium & Fluid

Hydration & Sweat Loss

Electrolyte & Fluid Calculator

Sweat carries away both water and sodium, and under-replacing either can raise cardiovascular strain and hurt performance, while over-drinking without electrolytes carries its own risks (Sawka et al, 2007).

Your fluid and sodium needs scale with body weight, heat, exercise intensity, and how long you're out there.

Select the options below to get a personalised estimate of how much to drink and how much sodium to take in.

Your body weight

70.0 kg = 154.3 lb. Use your race-day weight for the most accurate estimate.

Duration

60 minutes.

Heat / conditions

I'm a "salty sweater" (visible salt stains, salty taste)

Intensity

Your serving

Per hour

—

Fluid

Per hour

—

Sodium

Whole session

—

Fluid, total

Whole session

—

Sodium, total

Estimate · adjust to your own sweat rate over time

Based on general ranges from Sawka et al., 2007, Medicine & Science in Sports & Exercise (ACSM Position Stand). Individual sweat and sodium loss varies — for long or hot sessions, a personal sweat-rate test (weigh before/after) is the gold standard.

How to Stay Hydrated: 5 Expert Tips That Actually Work (Backed By Science)

Start already hydrated. Don't wait until a session begins, drink around 2 to 3 cups of water in the couple of hours beforehand, topped up with a smaller amount in the last 10 to 20 minutes.
Sawka et al., 2007, Medicine & Science in Sports & Exercise
Drink on a schedule, not just when thirsty. By the time you feel thirsty, fluid losses are already adding up. Sipping small amounts every 10 to 20 minutes keeps you ahead of it instead of playing catch-up.
McDermott et al., 2017, Journal of Athletic Training
Add sodium once sessions get long, hot, or hard. Water alone can't replace what's lost in sweat during longer or high-intensity efforts, a bit of sodium alongside your fluids helps you actually retain and absorb it.
Shirreffs & Sawka, 2011, Journal of Sports Sciences
Use body weight to check your replacement rate. Weighing yourself before and after a session is a simple, individual way to see how much you actually lose, sports-medicine guidance points to replacing roughly 1.5 litres of fluid per kilogram lost.
Casa et al., 2000, Journal of Athletic Training
Keep rehydrating after you stop. Sweat losses and urine output continue for a while post-exercise, so fluid and sodium intake shouldn't stop the moment you do, spread replacement out over the following hours.
Maughan & Shirreffs, 1997, Journal of Sports Sciences