# Calc vs GDDTracker

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.

Both are free to download. GDDTracker sells 2 in-app purchases, starting at $0.99 per month. Calc asks for nothing beyond the download.

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.

## The numbers

| Metric | Calc | GDDTracker |
| --- | --- | --- |
| Price | Free | Free |
| Rating | — | **[4.7 (13 ratings)](https://appshunter.io/ios/app/gddtracker/id6752981800/reviews)** |
| Number of ratings | — | **13** |
| Positive reviews | 66.7% of reviews | **100.0% of reviews** |
| In-app purchases | **No** | Yes |
| Ads | No | No |
| Update frequency | Every 21 months | **Every 2 days** |
| Monetization | **Free** | Subscription |
| Size | 36 MB | 15 MB |
| Requires iOS | **16.4** | 17.6 |
| Devices | iPhone, iPad | iPhone, Apple Watch |
| Age rating | 4+ | 4+ |
| Developer | [FTI (1997) Pty Ltd](https://appshunter.io/developer/462573989) | [Kirk Faris](https://appshunter.io/developer/1842027731) |

## What reviewers say

### Calc

[App page](https://appshunter.io/ios/app/calc-fdi/id530077646)

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:** macOS Compatibility, Vision Pro support

**In-app purchases:** none


### GDDTracker

[App page](https://appshunter.io/ios/app/gddtracker/id6752981800)

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:** Apple Watch app

**In-app purchases (2)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Monthly | $0.99 | per month |
| Annual | $9.99 | per year |


## Frequently asked 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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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*