# Hydrology Formulator vs Compare Flow

The clearest difference is review sentiment: Compare Flow at 50% against Hydrology Formulator's 0%. Compare Flow also leads on in-app purchases (none vs 1) and ratings volume (5 vs 1). Hydrology Formulator's advantage is rating (5.0 vs 4.6) and update cadence (every 6 months vs every 32 months). On price, ads, monetization model and device support there is nothing between them.

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

Hydrology Formulator holds the better App Store score, 5.0 against 4.6. That said, the two scores are not equally well evidenced: Compare Flow has 5 ratings behind it against 1, so its average is the more settled of the two. Written reviews complicate that: 0% of Hydrology Formulator's written reviews are positive against 50% of Compare Flow's, so the app with the better star average is not the one people write more warmly about.

Hydrology Formulator ships an update every 6 months, Compare Flow every 32 months. The most recent releases landed on October 8, 2026 and October 4, 2026 respectively.

## The numbers

| Metric | Hydrology Formulator | Compare Flow |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[5.0 (1 ratings)](https://appshunter.io/ios/app/hydrology-formulator/id346512904/reviews)** | [4.6 (5 ratings)](https://appshunter.io/ios/app/compare-flow/id581217854/reviews) |
| Number of ratings | 1 | **5** |
| Positive reviews | 0.0% of reviews | **50.0% of reviews** |
| In-app purchases | Yes | **No** |
| Ads | No | No |
| Update frequency | **Every 6 months** | Every 32 months |
| Monetization | Free | Free |
| Size | 18 MB | 23 MB |
| Requires iOS | 18.6 | **15.1** |
| Devices | iPhone, iPad | **iPhone, iPad, iPod** |
| Age rating | 4+ | 4+ |
| Developer | [Historycentral.com](https://appshunter.io/developer/1744330560) | [iENGINEERING Corporation](https://appshunter.io/developer/419618955) |

## 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 |


### Compare Flow

[App page](https://appshunter.io/ios/app/compare-flow/id581217854)

This application helps engineers and designers evaluate the hydraulic flow capacity of various non-pressure sewer pipe types. It allows for comparisons between different pipe geometries and materials, including concrete, thermoplastic, and metal options.

**Highlights:** Manning's Formula calculation, Compare hydraulic flow capacity, Evaluate pipe geometry alternatives, Compare pipe material options, Supports concrete, thermoplastic, and metal pipes, Circular, elliptical, arch, and box sections

**Features:** macOS Compatibility

**In-app purchases:** none


## Frequently asked questions

### Is Hydrology Formulator free?

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

### Is Compare Flow free?

Compare Flow is free to download, with no in-app purchases.

### Which has better reviews, Hydrology Formulator or Compare Flow?

Hydrology Formulator is rated higher. Hydrology Formulator averages 5.0 out of 5 from 1 ratings, while Compare Flow averages 4.6 from 5 ratings.

### Do Hydrology Formulator or Compare Flow have ads?

Neither Hydrology Formulator nor Compare Flow shows ads.

### Which is updated more often, Hydrology Formulator or Compare Flow?

Hydrology Formulator ships an update every 6 months, and Compare Flow every 32 months. Most recently, Hydrology Formulator was updated on October 8, 2026 and Compare Flow on October 4, 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.*