Energy Availability Calculator
Calculate reported energy availability per kilogram of fat-free mass, with a signed energy balance and intake sensitivity scenarios.
Sports energy balance workspace
Reported energy accounting; no RED-S diagnosis
Your reported energy availability
33.33 kcal/kg FFM/day
Reported intake minus net exercise energy, per fat-free kg
Full result table
| Intake kcal/day | Net exercise kcal/day | Remainder kcal/day | kcal/kg FFM/day |
|---|---|---|---|
| 2,400 | 600 | 1,800 | 30 |
| 2,600 | 600 | 2,000 | 33.333333 |
| 2,800 | 600 | 2,200 | 36.666667 |
A descriptive estimate from reported inputs, not a RED-S diagnosis or a universal safe-intake assessment. Intake, exercise energy and fat-free mass can each be uncertain. The tool does not apply a single clinical threshold to all sexes, sports or individuals.
Let’s work it out.
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How to use Energy Availability Calculator
- Use the same day for reported food energy and exercise expenditure.
- The waterfall shows intake, exercise subtraction and the remaining energy amount.
- The comparison varies intake by 200 kcal while preserving exercise and fat-free mass.
Worked example
At 2,600 kcal intake, 600 kcal net exercise expenditure and 60 kg fat-free mass, EA = 2,000/60 = 33.333333 kcal/kg FFM/day.
Formula, accuracy & limitations
EA = (dietary intake − net exercise energy expenditure) / fat-free mass. Intake and expenditure use kcal/day; fat-free mass uses kg. Negative values are kept visible.
A descriptive estimate from reported inputs, not a RED-S diagnosis or a universal safe-intake assessment. Intake, exercise energy and fat-free mass can each be uncertain. The tool does not apply a single clinical threshold to all sexes, sports or individuals.
These outputs use the stated model and your supplied inputs. A mathematically consistent model can still differ from personal measurements. Scenario curves and formula comparisons are not statistical confidence intervals.
Source and method context ↗Match the three inputs to one day
Use the same day for reported food energy and exercise expenditure. Exercise energy should represent the amount above rest, not total daily expenditure. Enter fat-free mass from an appropriate measurement or estimate, and keep kilograms separate from total body weight.
Read the signed result honestly
The waterfall shows intake, exercise subtraction and the remaining energy amount. The main value divides that remainder by fat-free mass. If subtraction is negative, the engine preserves it; replacing a negative result with zero would hide an input problem or a large reported imbalance.
Treat the sensitivity view as arithmetic
The comparison varies intake by 200 kcal while preserving exercise and fat-free mass. These are scenarios, not intake prescriptions. Energy availability research does not justify diagnosing an individual from one self-reported day, and the page does not assign universal green or red risk zones.
Avoid subtracting resting expenditure twice
Suppose a recorded workout shows 700 kcal of total energy, including 100 kcal that would have been spent at rest over that interval. A net-exercise input of 600 kcal matches this worksheet’s definition; entering the full 700 changes the remainder. The calculator does not know which convention your device uses, so it cannot perform that correction automatically. Use a consistent definition across diary days, and keep any interpretation of low availability separate from this input-accounting issue.
Frequently asked questions
Is energy availability the same as calorie balance?
This metric subtracts net exercise energy from intake, then divides by fat-free mass. It does not subtract every component of daily energy expenditure.
Should I enter my wearable daily total as exercise?
A full-day total includes resting and other activity energy. The exercise input here asks for net exercise energy above rest, so mixing them changes the meaning.
Why is there no RED-S risk score?
A diagnosis cannot be established by this arithmetic alone. The tool reports the defined quantity without inventing a personal medical category.
Why use fat-free mass rather than total weight?
That denominator belongs to the energy-availability definition used here. Substituting total mass produces a different quantity.
