Comparison

Calc vs GDDTracker

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

Head to head
About

Calc

This app assists Australian Bush Fire Control Officers and Brigade members in predicting fire behavior using the Australian Fire Danger Rating System. It calculates various fire metrics for different environments and works offline.

Highlights
  • Predicts fire behavior for Australian environments
  • Calculates Fire Danger Ratings
  • Estimates Rate of Spread
  • Estimates Flame Height
  • Uses Australian Fire Danger Rating System models
  • Works offline
Features
Read full description

CALC-FDI3 is designed to be used in Australia by Bush Fire Control Officers and members of Bush Fire Brigades. It makes use of the Australian Fire Danger Rating System models to predict fire behaviour for fires in the following environments: Grassland, Mallee Heath, Shrubland, Tasmanian Buttongrass, Spinifex and Spinifex Woodlands and Savanna Woodlands and Eucalypt Forests. Calculate Fire Danger Ratings, Fire Behaviour Index, Rate of Spread, Flame Height and more. Works offline. CALC-FDI3 uses models are those released in conjunction with the new nation-wide Fire Danger Rating system commencing September 1st 2022

About

GDDTracker

This app calculates Growing Degree Days (GDD) using hyper-local weather data to help you precisely time lawn care applications. It also logs applications, provides smart reminders, and includes profiles for over 50 grass varieties.

Highlights
  • Growing Degree Day (GDD) calculation and forecasting
  • Application logging with product details and notes
  • Smart reminders based on GDD, days, or soil temp
  • 50+ grass variety profiles
  • Rate calculator for product amounts
  • Multiple lawn management
  • CSV/PDF record export
Features
Read full description

GDD Tracker is the complete lawn care companion for homeowners and pros who want precision timing and organized records. Using your location and hyper-local weather data, the app calculates Growing Degree Days (GDD) so you know exactly when to apply pre-emergents, post-emergents, plant growth regulators, fertilizers, and more. But GDD Tracker goes beyond just tracking — it's a full-featured lawn management tool. GDD Tracking & Forecasting • Accurate GDD calculations based on your location and daily temps • Forecasted date to hit your target threshold • Clear progress with percentage, badge, and cumulative/daily charts • No-spray advisories for high wind, heat, or rain Application Log • Log every application — PGR, fertilizer, weed control, fungicide, insecticide, and more • Track products, rates, and notes for each entry • View season history with year-over-year comparisons • Export your records as CSV or PDF Smart Reminders • Get notified when it's time to reapply • Set reminders by GDD accumulation, calendar days, or soil temperature • Early warning alerts as you approach your threshold Built for Your Lawn • 50+ grass variety profiles — Bermuda, Zoysia, Fescue, Bluegrass, and more • Rate calculator for exact product amounts based on lawn size • Soil temperature estimates for pre-emergent and seeding timing • Manage multiple lawns with separate locations, settings, and color tags Everywhere You Need It • Widgets for your Home Screen • Apple Watch app for a quick glance • iCloud sync across all your devices • Optional device location or locked "home" coordinates Privacy-First No ads. No data selling. Location is used only to fetch local weather. iCloud sync is optional. How it works: 1. Add your lawn and choose your grass type or set a custom threshold. 2. Set your start date (e.g., last application). 3. Track daily progress as GDD accumulates. 4. Log applications and get notified when it's time to reapply. Perfect for: • Homeowners aiming for a healthier, weed-free lawn • DIY lawn enthusiasts who want precision timing • Lawn care pros who manage multiple properties and schedules Subscription Information GDD Tracker Pro is required to access all features. Two auto-renewing subscription options are available: • Monthly: $0.99/month • Annual: $9.99/year The annual plan includes a 7-day free trial. Payment will be charged to your Apple ID account at confirmation of purchase. Subscriptions automatically renew unless canceled at least 24 hours before the end of the current period. Your account will be charged for renewal within 24 hours prior to the end of the current period. You can manage and cancel your subscriptions by going to your App Store account settings after purchase. Privacy Policy: https://gdd-tracker.com/privacy Terms of Use (EULA): https://www.apple.com/legal/internet-services/itunes/dev/stdeula/ Download GDD Tracker and take the guesswork out of lawn care.

Screenshots

Calc4 screens
GDDTracker4 screens

Verdict

The call

The clearest difference is in-app purchases: Calc at none against GDDTracker's 2. GDDTracker's advantage is review sentiment (100% vs 67%) and update cadence (every 2 days vs every 21 months). On price, ads, device support and iOS requirement 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. GDDTracker sells 2 in-app purchases, starting at $0.99 per month. Calc asks for nothing beyond the download.

UpkeepUpdate frequency

Calc ships an update every 21 months, GDDTracker every 2 days. The most recent releases landed on November 1, 2026 and October 30, 2026 respectively.

Scorecard4 real differences · 6 level
Calc versus GDDTracker: the parameters behind the verdict, then further details
ParameterCalcGDDTracker
PriceFreeFree
Rating—4.7 (13 ratings) — better
Positive reviews66.7% of reviews100.0% of reviews — better
Number of ratings—13 — better
Update frequencyEvery 21 monthsEvery 2 days — better
AdsNoNo
In-app purchasesNo — betterYes
MonetizationFree — betterSubscription
DevicesiPhone, iPadiPhone, Apple Watch
Requires iOS16.4 — better17.6
Further details — not scored
Size36 MB15 MB
Age rating4+4+
DeveloperFTI (1997) Pty LtdKirk Faris

Customer experience

Calc

Written reviews3 reviews
Positive66.7%
Neutral33.3%
Negative0.0%

GDDTracker

All ratings13 ratings
Positive92.3%
Neutral0.0%
Negative7.7%
Written reviews7 reviews
Positive100.0%
Neutral0.0%
Negative0.0%

In-app purchases

None

Calc

No in-app purchases

2 purchases

GDDTracker

Subscriptions2
  • Monthly$0.991 Month
  • Annual7 Days trial$9.991 Year

Questions

Is Calc free?
Calc is free to download, with no in-app purchases.
Is GDDTracker free?
GDDTracker is free to download, with in-app purchases available.
Do Calc or GDDTracker have ads?
Neither Calc nor GDDTracker shows ads.
Which is updated more often, Calc or GDDTracker?
Calc ships an update every 21 months, and GDDTracker every 2 days. Most recently, Calc was updated on November 1, 2026 and GDDTracker on October 30, 2026.

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