# Hydrology Formulator vs Open Channel Flow Lite

The clearest difference is in-app purchases: Open Channel Flow Lite at none against Hydrology Formulator's 1. Open Channel Flow Lite also leads on iOS requirement (15.0 vs 18.6). On price, update cadence, ads and device support there is nothing between them.

Both are free to download. Hydrology Formulator sells 1 one-off in-app purchase. Open Channel Flow Lite asks for nothing beyond the download.

Hydrology Formulator ships an update every 6 months, Open Channel Flow Lite every 13 months. The most recent releases landed on October 24, 2026 and October 14, 2026 respectively.

## The numbers

| Metric | Hydrology Formulator | Open Channel Flow Lite |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[5.0 (1 ratings)](https://appshunter.io/ios/app/hydrology-formulator/id346512904/reviews)** | — |
| Number of ratings | **1** | — |
| Positive reviews | 0.0% of reviews | — |
| In-app purchases | Yes | **No** |
| Ads | No | No |
| Update frequency | **Every 6 months** | Every 13 months |
| Monetization | Free | — |
| Size | 18 MB | 2 MB |
| Requires iOS | 18.6 | **15.0** |
| Devices | iPhone, iPad | **iPhone, iPad, iPod** |
| Age rating | 4+ | 4+ |
| Developer | [Historycentral.com](https://appshunter.io/developer/1744330560) | [Alexius Academia](https://appshunter.io/developer/1209840214) |

## What reviewers say

### Hydrology Formulator

[App page](https://appshunter.io/ios/app/hydrology-formulator/id346512904)

This app provides a comprehensive collection of over 1,000 formulas, calculators, and conversions for hydrology and civil engineering. It covers a wide range of topics including groundwater, stormwater, pipe flow, and water pollution.

**Highlights:** 1,000+ formulas and calculators, Groundwater analysis tools, Stormwater design calculations, Open channel and pipe flow equations, Water pollution modeling, Conversions and reference data

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Pro Version | $3.99 | one-time |


### Open Channel Flow Lite

[App page](https://appshunter.io/ios/app/open-channel-flow-lite/id1579229822)

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases:** none


## Frequently asked questions

### Is Hydrology Formulator free?

Hydrology Formulator is free to download, with in-app purchases available.

### Is Open Channel Flow Lite free?

Open Channel Flow Lite is free to download, with no in-app purchases.

### Do Hydrology Formulator or Open Channel Flow Lite have ads?

Neither Hydrology Formulator nor Open Channel Flow Lite shows ads.

### Which is updated more often, Hydrology Formulator or Open Channel Flow Lite?

Hydrology Formulator ships an update every 6 months, and Open Channel Flow Lite every 13 months. Most recently, Hydrology Formulator was updated on October 24, 2026 and Open Channel Flow Lite on October 14, 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.*