# SI Calculator Pro — LSI / RSI Calculator

> LSI / RSI Calculator (iPhone/iPad app by Select Chemicals Limited.)

- Source: https://appshunter.io/ios/app/si-calculator-pro/id1568227316 (this page in markdown: same URL + `.md`)
- Developer: [Select Chemicals Limited](https://appshunter.io/developer/1538878240)
- Category: Utilities, Productivity
- Price: Free
- Age rating: 4+
- Requires: iOS 12.4 · 15 MB
- Languages: English
- Released: 2021-05-25
- Data updated: 2026-05-16
- User reviews in markdown: https://appshunter.io/ios/app/si-calculator-pro/id1568227316/reviews.md

## What is SI Calculator Pro?

PLEASE NOTE THAT THIS APP IS INTENDED FOR SCL CUSTOMERS ONLY AND WILL REQUIRE YOU TO MAKE AN ACCOUNT TO USE THIS APP.

Take the guess work out of your water chemistry by using SI Calculator Pro to get your desired water chemistry.

This App is a Saturation Index Calculator that will give you your LSI and RSI values. Simply input your waters current chemistry values then tweak the Hardness and Alkalinity Fields in the desired column to get the perfect water chemistry.

SI Calculator Pro can predict the values of the pH and Conductivity after adjusting the Hardness and Alkalinity fields.

SI Calculator Pro adds more functionality compared to our original SI Calculator app.
Hardness, Alkalinity, Cyanuric Acid and Chlorine calculators have all been added to SI Calculator Pro.


## Version history (last 2 releases)

### 5.5 — 2023-06-09

Feature Added:
   -Users can now approve themselves using a promotional code system.

Fixes:
   -General bug fixes.

### 5.2 — 2022-08-20

Fixes:
 - Refined calculations.
 - Changes made to number rounding.
 - Unit changes to help with readability.
 - Login Error handling.

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## Related topics

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-05-16.*