Chlorine Dosage Calculator

Calculator inputs

The page stays in a single-column flow, while the input fields switch to 3 columns on large screens, 2 on medium, and 1 on mobile.

Flow rate

Flow unit

Chlorine demand (mg/L)

Target residual (mg/L)

Safety factor (%)

Product strength (%)

Product density (kg/L)

Contact time (minutes)

Injection hours per day

Tank or batch volume

Tank volume unit

Example data table

Scenario	Flow	Demand	Residual	Strength	Applied Dose	Product Volume
Small clear water tank	250 m³/day	0.80 mg/L	0.50 mg/L	12.5%	1.43 mg/L	2.3833 L/day
Medium treatment line	800 m³/day	1.10 mg/L	0.60 mg/L	10%	1.87 mg/L	12.4667 L/day
High demand surface water	1,500 m³/day	1.80 mg/L	0.70 mg/L	12%	2.86 mg/L	29.7917 L/day
Compact disinfection skid	45 m³/day	0.35 mg/L	0.25 mg/L	15%	0.66 mg/L	0.1650 L/day

Formula used

1) Required chlorine dose

Required Dose (mg/L) = Chlorine Demand + Target Residual

2) Applied dose with operating buffer

Applied Dose (mg/L) = Required Dose × (1 + Safety Factor / 100)

3) Pure chlorine mass per day

Pure Chlorine (kg/day) = Applied Dose × Flow (m³/day) / 1000

4) Commercial product requirement

Product Mass (kg/day) = Pure Chlorine / Strength Fraction

5) Solution feed volume

Product Volume (L/day) = Product Mass / Product Density

6) CT value

CT (mg·min/L) = Target Residual × Contact Time

How to use this calculator

Step 1: Enter the operating flow and choose the correct flow unit.

Step 2: Enter chlorine demand measured from testing or recent plant data.

Step 3: Enter the free residual you want to maintain after contact time.

Step 4: Add a safety factor if your source water changes or dosing needs a buffer.

Step 5: Enter product strength and density for bleach, hypochlorite, or another chlorine solution.

Step 6: Enter contact time, batch volume, and daily injection hours.

Step 7: Click the calculate button to show results above the form.

Step 8: Export the results as CSV or PDF and review the graph for flow sensitivity.

Frequently asked questions

1) What does chlorine dosage mean?

It is the amount of chlorine added to water to meet demand and still leave the desired residual after contact time.

2) Why separate demand and residual?

Demand represents chlorine consumed by reactions in the water. Residual is the remaining disinfectant you want after those reactions finish.

3) Why is product strength important?

Commercial chlorine products are not pure chlorine. Lower strength solutions require more chemical mass and more feed volume for the same applied dose.

4) Why does density affect liters per day?

Density converts chemical mass into liquid volume. Two products may deliver the same chlorine mass but require different feed volumes.

5) What is CT value?

CT is the product of disinfectant residual and contact time. It is commonly used to compare disinfection exposure in treatment processes.

6) Can I use this for sodium hypochlorite bleach?

Yes. Enter the bleach strength as available chlorine percentage and use the appropriate solution density from your product data sheet.

7) Is this enough for compliance reporting?

No. It is a planning and estimation tool. Compliance decisions should also use verified sampling, operator judgment, plant testing, and local regulations.

8) Which flow unit should I choose?

Choose the unit that matches your plant records. The calculator converts everything internally to cubic meters per day for consistency.