JJB Performance

Are You Eating
Enough to Perform?

Most women in fitness are underfuelling without knowing it. This calculator estimates your energy availability — the single most important metric the industry ignores.

Takes about 90 seconds. Your personalised results require an email.

Based on

Loucks et al.

Used in

Clinical RED-S screening

Built by

JJB Performance

Step 1 of 4

Your body composition

We need your weight and approximate body fat percentage to calculate fat-free mass — the denominator in the energy availability equation.

Body weight (kg)

Estimated body fat %

Most women range 20–35%. A DEXA scan gives the most accurate number, but an estimate works here.

Step 2 of 4

Daily energy intake

Your average daily calorie intake. If you track, use that number. If not, estimate as best you can.

Average daily calories (kcal)

Step 3 of 4

Your training

Select every type of exercise you do in a typical week, then set duration and frequency for each.

Assessment Complete

Your Energy Availability

0

kcal / kg FFM / day

Your full report includes:

✓

Complete breakdown of your numbers (FFM, intake, expenditure)

✓

What your score means for hormonal health and performance

✓

The 7 RED-S warning signs most women miss

✓

A step-by-step intake adjustment framework

First name

Email address

No spam. Evidence-based coaching from JJB Performance.

Your Full Results

Energy Availability Breakdown

kcal / kg FFM / day

Low (<30)Reduced (30–45)Optimal (45+)

Your numbers

What this means

Energy availability below 30 kcal/kg FFM/day disrupts the HPG axis, reduces bone formation markers, impairs immune function, and degrades training adaptation. Most women in this range don't know they're underfuelling — they just feel tired, lose their period, get injured more, or plateau.

What happens next