Digital LSI Calculator
Easily calculate your pool’s LSI using Taylor’s online tool
What Is a Langelier Saturation Index (LSI) Calculator?
The Langelier Saturation Index (LSI) plays a key role in protecting your pool’s surfaces and equipment from damage and extending the life of plaster, tile, pumps, and heaters. A little routine monitoring and maintenance goes a long way in avoiding expensive repairs or replacements and keeping skin irritation and eye discomfort to a minimum.
The Taylor LSI calculator is a digital tool that provides a quick and accurate read of your pool or spa’s water balance. Easily determine if your water is corrosive, scale-forming, or right on target, so every swim feels comfortable and clean.
Calculate Now to See If Your Water Is:
- Corrosive Damaging to surfaces and equipment
- Balanced Ready to swim!
- Scale-forming Cloudy water and crusty deposits
Know before you dive in. Understanding your LSI helps you maintain balanced water, which may help protect your pool's plaster and tile, extend the life of your heater and pump, reduce the risk of unnecessary repairs, and keep your water more comfortable.
What Is The Saturation Index?
The Langelier Saturation Index (LSI) tells whether water is scaling or corrosive and helps find the perfect balance.
What Does The LSI Mean?
| SI | Condition | Risk |
|---|---|---|
| −0.30 or lower | Corrosive | Pitting or etching of plaster Metal corrosion |
| −0.30 to +0.30 (close to zero) | Balanced ✓ | Ideal range No treatment needed |
| +0.50 or higher | Scaling | Cloudy water Scale on surfaces |
Water Temperature And LSI
Water temperature can significantly impact water balance, so it's important to check the LSI in the summer and winter and after refilling the pool.
Borate and Carbonate Alkalinity
Borates are often added to improve pH stability and water clarity. However, borates also contribute to buffering capacity in a similar way to carbonates. Because standard total alkalinity tests measure both, the reported alkalinity value can be higher than the carbonate alkalinity used in the LSI calculation.
If your water contains borates, enable the "Uses Borate" option in the configuration and enter the current borate level. The calculator will adjust the total alkalinity by removing the borate contribution, allowing the LSI to be calculated using the true carbonate alkalinity.
As a result, the LSI calculated with borates enabled may differ from the LSI calculated without borate adjustment.
How To Adjust LSI
Adjusting TA affects pH so retest after each change.
2. pH — Second priority.
3. Calcium Hardness (CH) — Adjust last.
After you've made the necessary adjustments, retest to see if the water is balanced.
Chemical Adjustments Reference
Target Ranges
| Parameter | Pool | Spa |
|---|---|---|
| pH | 7.4 – 7.6 | 7.4 – 7.6 |
| Total Alkalinity | 80 – 120 ppm | 80 – 120 ppm |
| Calcium Hardness | 200 – 400 ppm | 150 – 250 ppm |
| CYA (Stabilizer) | 30 – 50 ppm | Not recommended |
| Borate | 30 – 50 ppm | 30 – 50 ppm |
| TDS | < 2000 ppm | Dump regularly |
| Temperature | 78°–82°F (25–28°C) | ≤ 104°F (40°C) |
Example
Result: SI ≈ −0.6 → Corrosive. Action required.
Solution: Hold pH and TA constant; raise Calcium Hardness from 50 to 200 ppm (+150 ppm) using Calcium Chloride. The 50 ppm CH was below recommended guidelines — hardness adjustment was the correct choice here.
How to Use Our LSI Calculator
Get an accurate LSI reading and guidance on next steps in seconds with Taylor’s digital LSI calculator.* The tool is built for pool owners and professionals alike and offers modern convenience, faster calculations, and less room for error.
Enter your latest test results
Provide the required information using the numbers from your most recent water test.
Get instant results and guidance
Your LSI score appears right away along with clear next steps on how to adjust if necessary.
Balance your water
Review the steps provided by the tool to get your water back to balanced.
Why Use a Digital LSI Calculator?
Knowing how to calculate LSI manually takes real skill, and it can also be time consuming and prone to errors. Our digital LSI calculator streamlines the process with an intuitive interface and step-by-step instructions that help you assess water balance without the guesswork. The technology is designed to maintain the accuracy that Taylor is known for, so you can make smarter decisions with trusted results every time.
A Simple Switch from the Taylor Watergram®
For decades, our printed Watergram® has been a dependable pool water balance calculator. Our digital calculator offers the same reliability with added ease and speed. It’s part of our ongoing commitment to upgrading trusted industry tools while maintaining the accuracy you depend on.
Think of it as the printed tool you already know, now available wherever you go.
Faster, Easier, More Reliable
No manual alignment or calculations. Just enter your test values and get instant results.
Reduce errors and save valuable time.
Accessible from any device, including smartphones, tablets, and computers.
Perfect for quick on-site checks, education and training, and record-keeping for pool professionals.
Ideal for routine maintenance checks.
*Disclaimer: Results are estimates based on the information entered and are intended to assist in evaluating water balance. They are not a substitute for appropriate water testing and professional advice. Always verify water chemistry using appropriate testing methods before making any water treatment decisions. Taylor does not warrant the accuracy, completeness, or applicability of these results.