Your physical
battery,
every morning
One number from 0 to 100. Capacity combines your sleep, HRV, and activity into a score that tells you exactly how hard to push today.
Free to download · iOS & Android · No account required
See it in action
Everything you need to know, at a glance
Daily score
One number from 0 to 100. Green means go hard, yellow means pace yourself, red means rest.
HRV detail
Track your heart rate variability over 7 days. See how sleep, training, and lifestyle affect your nervous system recovery.
Weekly Report PRO
Full breakdown of your week: daily scores, HRV trends, sleep quality, and pattern detection powered by your data.
How it works
Three steps, every morning
Open the app
Capacity reads your data from Apple Health or Health Connect automatically. No manual logging.
See your score
One number from 0 to 100. Green means go hard. Yellow means pace yourself. Red means rest.
Act on it
Personalized tips based on your score, baseline, and profile — not generic advice.
The science
100 points. 3 metrics.
Each metric is scored against your personal baseline, not population averages. The more you use Capacity, the smarter it gets.
Sleep
Hours, timing, and quality of your sleep stages (Deep, REM, Core).
HRV
Heart Rate Variability (RMSSD) — the most sensitive indicator of nervous system recovery.
Strain
Yesterday's activity: steps + active calories from wearable when available.
Capacity PRO
Go deeper with PRO
For athletes and biohackers who want to understand, not just track.
Weekly Report
Full breakdown of your week: HRV trends, sleep quality, strain vs baseline, and recovery score.
Adaptive Baseline
Your personal average updates as you train. The score reflects YOUR body, not the average person.
Training Readiness
Know exactly how ready you are to push hard today based on cumulative load and recovery.
Sleep Regularity
Consistency of your sleep schedule scored and charted over 30 days.
30-day History
See patterns in your recovery over a full month, not just the last 7 days.
Export Data
Export your full history as CSV for your own analysis or to share with a coach.
Pricing
Simple, honest pricing
Free
Core features, always free
- ✓Daily battery score
- ✓7-day trend
- ✓Sleep, HRV, Strain breakdown
- ✓Personalized tips
- ✓No ads, no tracking
PRO
Everything you need
- ★Everything in Free
- ★Weekly Report
- ★Adaptive baseline
- ★Training readiness
- ★Sleep regularity (30d)
- ★30-day history charts
- ★Export data as CSV
FAQ
Common questions
What is HRV and why does it matter? +
Heart Rate Variability (HRV) measures the time variation between heartbeats. Higher variability means your nervous system is adaptable and well-recovered. It's one of the best indicators of your readiness to train or handle stress.
Does Capacity work on Android? +
Yes. On Android, Capacity reads your data from Health Connect. You'll need a wearable (like a Fitbit, Galaxy Watch, or Pixel Watch) that syncs HRV and sleep data to Health Connect.
Is the app free? +
Capacity is free with core features: daily score, 7-day trend, and basic insights. Capacity PRO unlocks the weekly report, 30-day history, adaptive baseline, sleep regularity, and training readiness.
How do you calculate the Battery Score? +
The score is 100 points total: Sleep (32 pts) + HRV (45 pts) + Strain (23 pts). Each metric is scored against your personal baseline. The more data Capacity has, the more personalized your score becomes.
Does Capacity store my health data on servers? +
No. All your data stays on your device. We have no servers, no accounts, and no way to see your data. It's processed locally using Apple Health or Health Connect.
What wearable do I need? +
On iOS, Apple Watch gives the best results (HRV, sleep stages, active calories). iPhone alone works but without HRV. On Android, any wearable that writes to Health Connect works — Fitbit, Galaxy Watch, Garmin, etc.
Weekly recovery insights
HRV, sleep science, and training tips — every week. No spam, unsubscribe anytime.
From the blog
Learn more about recovery science
What is HRV and why your morning number matters
Heart Rate Variability is the most sensitive window into your nervous system. Here's what it means, how it changes daily, and what to actually do with it.
How to Tell If You're Overtraining (And What to Do About It)
Your body sends clear signals before overtraining becomes a real problem. Here's how to read them—and how Capacity makes it hard to miss.
How we calculate your Battery Score
A transparent look at the formula behind Capacity's daily score — Sleep (32 pts), HRV (45 pts), and Strain (23 pts).
Recently shipped 🚀
Full changelog →Your data stays yours
No servers. No accounts. No analytics. Your health data never leaves your device — processed locally using Apple Health and Health Connect.
Ready to know your energy?
Download Capacity for free and start your first morning in 30 seconds.