Free Tool

ENERGY AVAILABILITY ESTIMATOR

Explore the energy-availability formula without turning one estimate into a RED-S diagnosis.

BODY WEIGHT (KG)

BODY FAT %

DAILY CALORIE INTAKE

Average intake for the period you are comparing. Food logs commonly under-report.

DAILY EXERCISE ENERGY EXPENDITURE

Exercise only—not resting metabolism or normal daily activity. Use a comparable daily average.

CONCERNED ABOUT UNDER-FUELLING?

A calculator cannot diagnose RED-S.

Persistent symptoms, menstrual disturbance, low libido, recurrent illness or a bone stress injury need qualified medical and sports-dietetic assessment.

Read the evidence-based RED-S guide →

Quick answer

Enter daily energy intake, exercise energy expenditure, body weight and estimated body fat. The tool applies the standard energy-availability equation and returns an educational estimate in kcal per kg of fat-free mass. It does not screen for or diagnose RED-S.

WHAT IT DOES

Energy availability describes dietary energy remaining after exercise expenditure, scaled to fat-free mass. The equation is useful in research and can structure a fuelling conversation, but free-living food intake, exercise expenditure and body composition are difficult to measure accurately. This tool shows the arithmetic without converting it into a clinical traffic light.

WHO IT'S FOR

→Riders pursuing race weight
→High-volume cyclists reviewing how intake relates to exercise demand
→Anyone with persistent fatigue, frequent illness, or stalled progress
→Female cyclists with menstrual irregularity or stress fractures
→Coaches explaining the energy-availability concept without diagnosing an athlete

HOW IT WORKS

Energy Availability (EA) = (daily energy intake − exercise energy expenditure) ÷ fat-free mass. Values around 30 and 45 kcal/kg FFM/day are widely cited research reference points, largely derived from controlled work in young women. They are not universal diagnostic boundaries across sexes, sports, durations or individuals.

01
Choose a comparable period
Use an average that matches the same days for intake and exercise. A single unusually long ride or incomplete food day will distort the result.
02
Estimate intake
Record food and drink as carefully as practical, while recognising that self-reported energy intake in athletes commonly differs from reference measurements.
03
Enter exercise expenditure
Use exercise energy only, not total daily expenditure. Power-meter kilojoules may inform cycling estimates, but devices and metabolic assumptions still introduce error.
04
Estimate fat-free mass
Fat-free mass equals body weight minus estimated fat mass. DXA, bioimpedance and circumference methods are not interchangeable and each adds uncertainty.
05
Use the result as context
Do not label the value optimal, dangerous or diagnostic. Compare it with symptoms, health history, training and qualified assessment.

EXAMPLE CALCULATIONS

Female 60kg rider, 12hr/week training

· Intake: 2,400 kcal/day
· Training: 12 hr/week at 150W
· Weight: 60kg
· Body fat: 22%

The arithmetic produces an estimate near 28 kcal/kg FFM/day. Because the inputs and research boundaries are uncertain, this is a prompt to review the wider context—not a clinical category or automatic calorie prescription.

Male 75kg rider, 8hr/week training

· Intake: 3,200 kcal/day
· Training: 8 hr/week at 200W
· Weight: 75kg
· Body fat: 15%

The arithmetic produces an estimate near 46 kcal/kg FFM/day. It does not prove that intake is adequate or rule out a health problem.

LIMITATIONS

This is not a RED-S screener. Every input has meaningful error, and the 30/45 reference points do not operate as universal clinical cut-offs. The IOC REDs CAT2 uses screening, severity and risk assessment, exclusion of other causes, and a physician-led diagnosis informed by a multidisciplinary team.

When to see a coach

Seek qualified medical and sports-dietetic assessment for menstrual disturbance, low libido or sexual-function change, recurrent bone stress injury, persistent fatigue or illness, marked performance change, rapid weight change, disordered eating or distress around food and training. A coach and app can provide context but cannot make the diagnosis.

FREQUENTLY ASKED QUESTIONS

What is RED-S in cycling?+

Relative Energy Deficiency in Sport describes impaired health and performance associated with exposure to problematic low energy availability. It can affect female and male cyclists, but its indicators are non-specific and other causes must be considered. Diagnosis is physician-led, not calculator-led.

What is a healthy energy availability for cyclists?+

There is no single validated healthy cut-off for every cyclist. Values around 30 and 45 kcal/kg FFM/day are useful research references but responses vary with sex, duration, baseline status and measurement method. Health, symptoms and performance require wider assessment.

How is energy availability different from calorie deficit?+

Energy balance compares intake with total expenditure. Energy availability subtracts exercise expenditure from intake and scales the remainder to fat-free mass. They describe different concepts; neither a short food log nor body-weight stability can diagnose RED-S.

Can I diet for race weight without low energy availability?+

Body-composition goals should be individualised and should not compromise health or useful training. This estimator cannot set a safe deficit, duration, protein target or minimum body weight. Riders with symptoms, previous RED-S, bone stress injury or disordered eating need qualified support before pursuing weight loss.

How do I know if I have RED-S?+

You cannot diagnose RED-S from this estimate, one symptom, one blood test or one DXA result. The IOC CAT2 uses a three-step process culminating in physician-led diagnosis and treatment after other causes are considered. Seek assessment when indicators persist or health is affected.