# HydroCalc Basic vs SKLDSP25

The clearest difference is in-app purchases: SKLDSP25 at none against HydroCalc Basic's 1. SKLDSP25 also leads on iOS requirement (12.2 vs 15.1). HydroCalc Basic's advantage is update cadence (every 11 days vs every 8 months). On price, ads and device support there is nothing between them.

Both are free to download. HydroCalc Basic sells 1 one-off in-app purchase. SKLDSP25 asks for nothing beyond the download.

HydroCalc Basic ships an update every 11 days, SKLDSP25 every 8 months. The most recent releases landed on October 4, 2026 and October 15, 2026 respectively.

## The numbers

| Metric | HydroCalc Basic | SKLDSP25 |
| --- | --- | --- |
| Price | Free | Free |
| In-app purchases | Yes | **No** |
| Ads | No | No |
| Update frequency | **Every 11 days** | Every 8 months |
| Size | 35 MB | 59 MB |
| Requires iOS | 15.1 | **12.2** |
| Devices | **iPhone, iPad, iPod** | iPhone, iPod |
| Age rating | 4+ | 4+ |
| Developer | [Transparent Blue Water LLC](https://appshunter.io/developer/1847968351) | [伟 陈](https://appshunter.io/developer/1837176650) |

## What reviewers say

### HydroCalc Basic

[App page](https://appshunter.io/ios/app/hydrocalc-basic/id6752577110)

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

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Premium - Flow Units & Ad-Free | $1.99 | one-time |


### SKLDSP25

[App page](https://appshunter.io/ios/app/skldsp25/id6754279210)

**Features:** macOS Compatibility

**In-app purchases:** none


## Frequently asked questions

### Is HydroCalc Basic free?

HydroCalc Basic is free to download, with in-app purchases available.

### Is SKLDSP25 free?

SKLDSP25 is free to download, with no in-app purchases.

### Do HydroCalc Basic or SKLDSP25 have ads?

Neither HydroCalc Basic nor SKLDSP25 shows ads.

### Which is updated more often, HydroCalc Basic or SKLDSP25?

HydroCalc Basic ships an update every 11 days, and SKLDSP25 every 8 months. Most recently, HydroCalc Basic was updated on October 4, 2026 and SKLDSP25 on October 15, 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.*