Calculator Inputs
Use this to estimate how much each salt increases solution TDS.
Example Data Table
Use these sample values to validate the calculator.
| Baseline (ppm) | Batch | Salt 1 | Dose | Salt 2 | Dose | Expected Added (ppm) |
|---|---|---|---|---|---|---|
| 120 | 10 L | Calcium nitrate | 10 g | Magnesium sulfate | 5 g | 1500 |
| 40 | 1 US gal | Potassium nitrate | 4 oz | — | — | ~1058 |
Formula Used
ppm_added = (grams × 1000) ÷ liters
final_ppm = baseline_ppm + Σ(ppm_added)EC(mS/cm) ≈ final_ppm ÷ (ppm_per_mS)
How to Use
- Measure your source water and enter baseline TDS.
- Enter your batch volume and select its unit.
- Add each fertilizer salt and its exact dose.
- Choose the EC conversion factor your meter uses.
- Submit to see final ppm, EC, and per-salt shares.
- Download CSV or PDF for logs and repeatability.
Why TDS Matters in Irrigation Solutions
Total dissolved solids influences osmotic pressure, nutrient uptake, and salt stress. When the solution is too strong, roots must work harder to absorb water, which can slow growth and reduce yield. Monitoring baseline source water and the added contribution from salts helps you keep mixes consistent across batches.
Mass-Based Estimation Versus Meter Readings
This calculator estimates added ppm from mass per volume, using mg/L as a practical proxy for ppm. Handheld meters often derive TDS from electrical conductivity using a conversion factor. Selecting 500, 640, 700, or a custom factor aligns the displayed EC with your meter’s reporting style.
Interpreting Added ppm by Individual Salts
Each salt row converts your entered dose into grams, then distributes that mass across the batch liters to estimate ppm added. The breakdown table shows both the ppm contribution and the percentage of added TDS. This makes it easy to identify dominant contributors, compare alternative salts, and spot dosing errors before mixing larger reservoirs. In practice, salts differ in ion mobility, so meter readings may deviate slightly; use this estimate for planning, then confirm with measurements at mixing.
Using Targets to Manage Crop Sensitivity
If you enter a target TDS, the calculator reports the gap between your predicted final value and the target. A positive gap means the mix is below target, while a negative gap suggests you may be too concentrated. Targets are useful for stage-based feeding, cloning, seedlings, and salt-sensitive cultivars. For recirculating systems, apply targets after accounting for evaporation and top-off water, then recheck after full mixing.
Recordkeeping and Repeatable Mixing
Consistency improves troubleshooting. Exporting the report to CSV supports spreadsheets, batch logs, and audit trails. The PDF report is useful for sharing recipes with staff and documenting changes over time. Pair these records with periodic meter calibration and water temperature notes to maintain stable mixing practices. When results drift, compare baseline readings first, then validate scales, units, and lot changes to isolate the cause quickly.
FAQs
1) Is ppm the same as mg/L in this calculator?
For dilute nutrient mixes, ppm is commonly treated as mg/L. The calculator uses mass per volume to estimate mg/L, which is a practical planning approximation.
2) Why can my meter show a different TDS than the estimate?
Meters infer TDS from conductivity using a factor, and ion composition changes conductivity. Temperature, calibration, and incomplete dissolution also shift readings. Use the estimate for recipe design, then verify with your meter.
3) Which EC conversion factor should I choose?
Match the factor your meter uses. If unsure, compare a known solution’s EC and displayed TDS, then pick the factor that best reproduces your instrument’s behavior.
4) Can I enter multiple salts with different units?
Yes. Each row converts the dose into grams, then computes ppm from batch liters. Mixing mg, g, kg, ounces, and pounds is supported within the same recipe.
5) Does this account for water hardness or alkalinity?
No. Hardness, alkalinity, and specific ions affect plant response and pH management, but they are not separated here. Use baseline TDS plus your water report for deeper interpretation.
6) How should I use the target gap result?
Use it as a quick check for under- or over-strength mixes. If you are above target, reduce a dominant salt or increase batch volume. If below, increase doses gradually and re-measure.