Comparison

Zero Doubt Club vs Chart35

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

Head to head
About

Zero Doubt Club

This app helps you achieve your fitness goals by tracking workouts and meals with the guidance of a personal trainer. Monitor progress, manage nutrition, and stay motivated with real-time coaching and reminders. Connect wearable devices for seamless data syncing.

Highlights
  • Workout and meal tracking
  • Progress monitoring
  • Nutrition management
  • Real-time coach messaging
  • Body measurement tracking
  • Progress photo logging
  • Wearable device integration
Features
Read full description

With the Zero Doubt Club App, you can start tracking your workouts and meals, measuring results, and achieving your fitness goals, all with the help of your personal trainer. - Access training plans and track workouts - Schedule workouts and stay committed by beating your personal bests - Track progress towards your goals - Manage your nutrition intake as prescribed by your coach - Set health and fitness goals - Message your coach in real-time - Track body measurements and take progress photos - Get push notification reminders for scheduled workouts and activities - Connect to wearable devices like Apple Watch (synced to Health app), Fitbit and Withings to sync body stats instantly Download the app today!

About

Chart35

Features
Read full description

Chart35 is a private fertility-charting app for the Creighton Model FertilityCare System (CrMS). Record each day's observation, see your color-coded stamp and chart, and keep your record on your own device. YOUR DATA STAYS WITH YOU Chart35 is offline-first. Your observations live on your device and the app works with no connection. Account sync is optional. When you turn it on, your records are encrypted on your device before they are uploaded, so the server stores data it cannot read. CHART THE WAY YOU WERE TAUGHT - Color-coded stamps: red, green, white, and yellow, matching standard CrMS charting. - Observation codes for bleeding, mucus, and frequency, built from the codes you already use. - Peak Day and post-peak count tracking. - Chart and calendar views, with Normal, Compact, and Trend zoom to see one cycle or many at a glance. - Insights: cycle count, average cycle length, and a cycle-length trend at a glance. SHARE WITH YOUR PRACTITIONER Generate a read-only link to your chart for your FertilityCare Practitioner. The link is encrypted so the server cannot read the shared data, and you can revoke it at any time. BUILT FOR REVIEW Your notes stay private and are never included in a shared chart. You decide what syncs and what is shared. You can delete your account and data at any time. ABOUT THE METHOD Chart35 is a charting and record-keeping tool. It is not medical advice and does not interpret your fertility for you. The Creighton Model is learned with a certified FertilityCare Practitioner. Yellow-stamp (Base Infertile Pattern) use in particular should only follow a baseline established with your practitioner. To find a practitioner, see your instructor or a FertilityCare center. Chart35 is independent and is not affiliated with or endorsed by the Saint Paul VI Institute or the creators of the Creighton Model System. "Creighton Model" and "FertilityCare" refer to the method and are used to describe what the app charts.

Screenshots

Zero Doubt Club4 screens
Chart354 screens

Verdict

The call

The clearest difference is update cadence: Chart35 at every 6 days against Zero Doubt Club's every 2 months. On price, ads, in-app purchases and device support there is nothing between them.

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

CostPrice · In-app purchases · Ads · Monetization

Both are free to download. Neither carries in-app purchases, so what you see is what you pay.

UpkeepUpdate frequency

Zero Doubt Club ships an update every 2 months, Chart35 every 6 days. The most recent releases landed on October 4, 2026 and October 6, 2026 respectively.

Scorecard1 real difference · 8 level
Zero Doubt Club versus Chart35: the parameters behind the verdict, then further details
ParameterZero Doubt ClubChart35
PriceFreeFree
Rating5.0 (6 ratings) — better—
Number of ratings6 — better—
Update frequencyEvery 2 monthsEvery 6 days — better
AdsNoNo
In-app purchasesNoNo
MonetizationFree—
DevicesiPhone, iPad, iPod, Apple WatchiPhone, iPad, iPod, Apple Watch
Requires iOS15.115.0 — better
Further details — not scored
Size201 MB5 MB
Age rating4+4+
DeveloperZero Doubt Club Cleveland East LLCStephens Page LLC

In-app purchases

None

Zero Doubt Club

No in-app purchases

None

Chart35

No in-app purchases

Questions

Is Zero Doubt Club free?
Zero Doubt Club is free to download, with no in-app purchases.
Is Chart35 free?
Chart35 is free to download, with no in-app purchases.
Do Zero Doubt Club or Chart35 have ads?
Neither Zero Doubt Club nor Chart35 shows ads.
Which is updated more often, Zero Doubt Club or Chart35?
Zero Doubt Club ships an update every 2 months, and Chart35 every 6 days. Most recently, Zero Doubt Club was updated on October 4, 2026 and Chart35 on October 6, 2026.

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