Comparison

Flow Fasting Tracker vs Rhythmus

Price, ratings, monetisation and update history for both apps, side by side โ€” with what reviewers say about each.

Head to head
About

Flow Fasting Tracker

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Your cycle changes everything. Most fasting apps ignore it. Estrogen, progesterone and testosterone each shift your metabolism, energy and hunger differently across your cycle. Flow Fasting tracks where you are and guides your fasting practice around it, so you always know the right window for your phase, and why it works. Whether you struggle to fast during your luteal phase, feel unstoppable in follicular, or want to understand why your results change week to week - Flow Fasting gives you a science-backed approach for every phase of your cycle. FIVE PHASES. FIVE DIFFERENT FASTING STRATEGIES. Bleed: Rest and restore. Shorter windows, nourishing breaks. Follicular: Your peak window. Longer fasts, stronger results. Ovulatory: High energy. Maintain momentum and protect your gains. Early Luteal: Shift with your hormones. Moderate and consistent. Late Luteal: Listen to your body. Gentle windows, no force. WHAT'S INSIDE: Phase-synced fasting windows Fasting recommendations that adapt to your cycle every day. Built around your phase, your goals and your rhythm. Fasting timer A clean, focused timer with real-time milestone markers at 14, 16 and 24 hours. Know exactly where you are in your fast and what your body is doing. Cycle insights Charts that connect your fasts, weight and steps over time. Spot your patterns, track your progress and understand how your cycle shapes your results. Daily log Track weight, steps, symptoms, energy, mood and sleep every day. Watch your insights build as your data grows. Sync your steps from Apple Health with one tap. Toggle it on in Settings to see your activity alongside your fasting and cycle date. Phase nutrition guide What to eat in every phase of your cycle. Food directly affects how well you fast - Flow Fasting connects the two. By phase comparison See how your energy, mood, sleep and fasting performance compare across all five phases. Built from your own data over time. Week planner Plan your fasting windows ahead. Map your cycle, set your intentions and remove the daily guesswork. Science guide The research behind cycle-synced fasting. Hormones, metabolism, autophagy, cortisol and more - all explained through a cycle lens. START FREE: Try Flow Fasting free for 7 days with annual plan. Full access. After your trial, you will be charged $39.99 unless cancelled before the trial ends. Monthly plan available at $7.99 per month, billed immediately. Cancel anytime in App Store settings. For wellness purposes only. Not medical advice. Terms of use: https://flowfasting.com/terms-of-service/

About

Rhythmus

Features
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Rhythmus is a period tracker with a cycle calendar โ€” plus a nutrition and training plan that changes with your cycle. WHAT RHYTHMUS DOES โ€ข Cycle and period calendar: log your period, see your cycle day and phase at a glance, with estimated ovulation and fertile window โ€ข Nutrition plan: meals and nutrients matched to your current phase โ€“ omnivore, vegetarian, vegan โ€“ with a shopping list โ€ข Training plan: workouts scaled to your intensity and training days, logged set by set โ€ข Supplements: which nutrients matter in which phase โ€ข Daily energy check-in: feeling low, and the app suggests a gentler session โ€ข Weekly overview, symptom diary, cycle statistics from your own history WHO IT IS FOR For women who train and notice that the same session feels easy one week and impossible the next. Menstruation, follicular phase, ovulation and the luteal phase each ask for something different โ€” Rhythmus takes that into account. NO ACCOUNT, NO TRACKING No sign-up, no registration, no ads, no subscriptions, no in-app purchases. Everything you enter stays on your device and is sent nowhere. The app works fully offline. From Settings you can export a backup at any time and restore it on another device. WITH SOURCES Every health statement in the app comes with a citation you can tap โ€” straight to the study or fact sheet. Among others from the Journal of the International Society of Sports Nutrition, the Journal of Medical Internet Research and the National Institutes of Health. Available in German, English and Spanish. Rhythmus is a free passion project. Note: Rhythmus is not a medical device, not a contraception method, and does not replace medical advice.

Screenshots

Flow Fasting Tracker4 screens
Rhythmus4 screens

Verdict

The call

The clearest difference is in-app purchases: Rhythmus at none against Flow Fasting Tracker's 2. Rhythmus also leads on update cadence (daily vs every 10 days). Flow Fasting Tracker's advantage is iOS requirement (13.0 vs 15.0). On price, ads and device support there is nothing between them.

Scored on Price ยท Rating ยท Positive reviews ยท Number of ratings ยท Update frequency ยท Ads ยท In-app purchases ยท Monetization ยท Best chart rank ยท Devices ยท Requires iOS

CostPrice ยท In-app purchases ยท Ads ยท Monetization

Both are free to download. Flow Fasting Tracker sells 2 in-app purchases, starting at $7.99 per month. Rhythmus asks for nothing beyond the download.

UpkeepUpdate frequency

Flow Fasting Tracker ships an update every 10 days, Rhythmus daily. The most recent releases landed on October 13, 2026 and October 1, 2026 respectively.

Scorecard3 real differences ยท 3 level
Flow Fasting Tracker versus Rhythmus: the parameters behind the verdict, then further details
ParameterFlow Fasting TrackerRhythmus
PriceFreeFree
Update frequencyEvery 10 daysDaily โ€” better
AdsNoNo
In-app purchasesYesNo โ€” better
DevicesiPhone, iPad, iPod โ€” betteriPhone, iPod
Requires iOS13.0 โ€” better15.0
Further details โ€” not scored
Size16 MB20 MB
Age rating4+4+
DeveloperKristina KozicynaitePatrick Sarpen

In-app purchases

2 purchases

Flow Fasting Tracker

Subscriptions2
  • Monthly$7.991 Month
  • Annual7 Days trial$39.991 Year
None

Rhythmus

No in-app purchases

Questions

Is Flow Fasting Tracker free?
Flow Fasting Tracker is free to download, with in-app purchases available.
Is Rhythmus free?
Rhythmus is free to download, with no in-app purchases.
Do Flow Fasting Tracker or Rhythmus have ads?
Neither Flow Fasting Tracker nor Rhythmus shows ads.
Which is updated more often, Flow Fasting Tracker or Rhythmus?
Flow Fasting Tracker ships an update every 10 days, and Rhythmus daily. Most recently, Flow Fasting Tracker was updated on October 13, 2026 and Rhythmus on October 1, 2026.

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