Calculator
Example data table
| Water | Current (ppm) | Target (ppm) | Product | Strength | Estimated dose |
|---|---|---|---|---|---|
| 100 L | 0.0 | 2.0 | Bleach | 5.25% | ≈ 36.3 mL |
| 500 L | 0.5 | 3.0 | Cal hypo | 70% | ≈ 17.9 g |
| 1 m³ | 1.0 | 2.0 | Bleach | 10% | ≈ 92.6 mL |
Formula used
Free chlorine is expressed as ppm, which is the same as mg/L. The required increase is: ΔFC = Target − Current
Convert that increase into mass of available chlorine: mg needed = ΔFC × Volume(L) and g available chlorine = mg ÷ 1000
If your product has an available chlorine strength of S%, then the product mass is: g product = g available chlorine ÷ (S/100)
For liquid bleach, volume is estimated with density: mL bleach = g product ÷ density(g/mL)
How to use this calculator
- Measure your tank or batch water volume and choose units.
- Test current free chlorine with a reliable kit.
- Set a target level appropriate for your system.
- Select sanitizer type and enter its labeled strength.
- For bleach, keep density default unless you know it.
- Click Calculate, then review dose and equivalents.
- Mix slowly, circulate well, and re-test before watering.
- Use CSV or PDF export to save your mixing record.
Safety reminders
- Never mix chlorine products with acids or ammonia.
- Wear gloves and eye protection, and work outdoors.
- Start low, verify with testing, and adjust gradually.
Why free chlorine matters
Free chlorine (FC) is the active disinfecting fraction that helps reduce biofilm growth, algae, and microbial load in tanks, lines, and emitters. In garden systems, stable FC can support cleaner irrigation hardware and more consistent flow, especially in warm storage conditions. This calculator estimates the dose needed to move from a measured FC value to a target level.
Choosing a practical target
Targets depend on water quality, organic demand, and contact time. Cleaner source water typically needs smaller increases, while high turbidity, algae presence, or high organic content can consume chlorine quickly. Start with conservative targets, measure again after mixing, and adjust in small steps to avoid overshooting.
Interpreting product strength
Strength labels describe “available chlorine” as a percentage. Liquid bleach commonly ranges from 3% to 12.5%, while calcium hypochlorite granules are often 65% to 73%. The calculator converts your required ppm increase into grams of available chlorine, then divides by the strength fraction to estimate product mass or liquid volume.
Mixing, circulation, and verification
Dose calculations assume complete mixing. For best accuracy, add product slowly into circulating water, allow adequate contact time, then test FC at the point of use. If the optional half-life and contact time fields are used, the calculator provides a simple residual estimate to illustrate how FC may drop during holding and distribution.
Recordkeeping for repeatable results
Consistent dosing improves when you track volume, product strength, and measured before/after FC. Use the CSV export for logs, or save a PDF report for batch mixing records. Over time, your notes can reveal typical chlorine demand for different seasons, storage durations, and source changes, helping you dial in reliable garden routines.
FAQs
1) What does ppm mean in this calculator?
ppm equals mg/L for water. If you increase FC by 1 ppm in 1,000 liters, you add 1,000 mg (1 g) of available chlorine, assuming full mixing.
2) Why does my measured FC end up lower than the target?
Chlorine is consumed by organics, algae, metals, and sunlight. Losses can happen during mixing and holding. Re-test after circulation and adjust with a smaller follow-up dose.
3) Which sanitizer type should I select?
Select the product you will actually use. Bleach estimates volume using density. Calcium hypochlorite returns a granule mass. Chlorine gas option shows the equivalent pure available chlorine mass.
4) How accurate is the density setting for bleach?
Density varies with formulation and temperature. The default value provides a workable estimate. If you have a product datasheet, enter its listed density to improve mL accuracy.
5) Can I use this for greenhouse misting or foliar applications?
Use caution. Plants can be sensitive to oxidants. Start at low levels, confirm compatibility with your crop and equipment, and always verify with testing before applying to foliage.
6) Why export CSV or PDF?
Exports help you document batch details, repeat successful mixes, and troubleshoot problems. A simple record of volume, product strength, and FC readings can save time and reduce dosing errors.