Comparison

NFP Calendar vs Chart35

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

Head to head
About

NFP Calendar

Track your fertility naturally using various methods like Creighton or Billings. Record daily observations, manage your cycle, and export data for your instructor or doctor. Designed specifically for Natural Family Planning users.

Highlights
  • Record mucus observations
  • Track menstrual flow
  • Log intercourse timing
  • Automatic cycle detection
  • Generate PDF charts
  • Export data as JSON
  • iCloud sync
Features
Read full description

Track your fertility naturally with a beautiful, intuitive charting app designed for Natural Family Planning methods. NFP Calendar helps you record daily fertility observations following Creighton Model, Billings, or other mucus-based NFP methods. Whether you're trying to conceive or avoid pregnancy naturally, this app gives you everything you need to chart with confidence. DAILY CHARTING MADE SIMPLE - Record mucus observations: color, sensation, and stretch - Track menstrual flow intensity (heavy, moderate, light, spotting) - Log intercourse timing and frequency - Mark peak days and cycle starts - Add personal notes to any day POWERFUL CYCLE MANAGEMENT - Automatic cycle detection and numbering - Smart handling of spotting vs. true periods - View your complete cycle history at a glance - Navigate cycles easily with calendar and list views EXPORT & BACKUP - Generate beautiful PDF charts for your instructor or doctor - Export your data as JSON for backup - iCloud sync keeps your data safe across devices DESIGNED FOR NFP USERS Built specifically for fertility awareness methods, not just another period tracker. Every feature is tailored to the vocabulary and workflow of NFP charting. Your fertility data stays private on your device. No account required. Start charting your fertility journey today. Terms of Use (EULA): https://www.apple.com/legal/internet-services/itunes/dev/stdeula/ Privacy Policy: https://estebancervera.github.io/nfp-support/

About

Chart35

This app helps users privately track their fertility observations using the Creighton Model FertilityCare System. It offers offline functionality, color-coded stamps, and various chart views. Users can securely share their data with practitioners.

Highlights
  • Creighton Model charting
  • Offline-first functionality
  • Color-coded observation stamps
  • Chart and calendar views
  • Peak day and post-peak tracking
  • Secure practitioner sharing
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

NFP Calendar4 screens
Chart354 screens

Verdict

The call

The clearest difference is update cadence: Chart35 at every 6 days against NFP Calendar's every 2 months. Chart35 also leads on rating (5.0 vs 4.7) and device support (4 vs 2). NFP Calendar's advantage is ratings volume (3 vs 1). On price, ads, in-app purchases and monetization model 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.

ReceptionRating · Positive reviews · Number of ratings

Chart35 holds the better App Store score, 5.0 against 4.7. Both are backed by a comparable volume of ratings — 3 and 1 respectively.

UpkeepUpdate frequency

NFP Calendar ships an update every 2 months, Chart35 every 6 days. The most recent releases landed on October 22, 2026 and October 25, 2026 respectively.

Scorecard5 real differences · 5 level
NFP Calendar versus Chart35: the parameters behind the verdict, then further details
ParameterNFP CalendarChart35
PriceFreeFree
Rating4.7 (3 ratings)5.0 (1 ratings) — better
Positive reviews100.0% of reviews—
Number of ratings3 — better1
Update frequencyEvery 2 monthsEvery 6 days — better
AdsNoNo
In-app purchasesNoNo
MonetizationFreeFree
DevicesiPhone, iPadiPhone, iPad, iPod, Apple Watch — better
Requires iOS26.015.0 — better
Further details — not scored
Size8 MB5 MB
Age rating12+4+
DeveloperEsteban CerveraStephens Page LLC

In-app purchases

None

NFP Calendar

No in-app purchases

None

Chart35

No in-app purchases

Questions

Is NFP Calendar free?
NFP Calendar is free to download, with no in-app purchases.
Is Chart35 free?
Chart35 is free to download, with no in-app purchases.
Which has better reviews, NFP Calendar or Chart35?
Chart35 is rated higher. NFP Calendar averages 4.7 out of 5 from 3 ratings, while Chart35 averages 5.0 from 1 ratings.
Do NFP Calendar or Chart35 have ads?
Neither NFP Calendar nor Chart35 shows ads.
Which is updated more often, NFP Calendar or Chart35?
NFP Calendar ships an update every 2 months, and Chart35 every 6 days. Most recently, NFP Calendar was updated on October 22, 2026 and Chart35 on October 25, 2026.

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