Testing your pool water is only half the job — knowing exactly how much chlorine, pH adjuster, or alkalinity increaser to add is what actually gets your water back in balance. Enter your pool’s volume and current readings below to get an exact dose.
Pool Chemical & Chlorine Dosage Calculator
Find out how much chlorine, pH adjuster, or alkalinity increaser to add.
Don't know your gallons? Use our Pool Volume Calculator first.
Typical target: 3 ppm for regular maintenance, 10 ppm for shocking a green or cloudy pool.
Ideal range is 7.2–7.6.
Ideal range is 80–120 ppm.
Chlorine —
Add
Target is at or below current level — no chlorine needed.
Raises free chlorine by ppm.
pH Adjustment
Add
pH is already at target — no adjustment needed.
Total Alkalinity Adjustment
Add Baking Soda
TA is already at or above target — no increase needed.
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How Pool Chemical Dosing Works
Pool chemical dosing comes down to one core idea: the amount of chemical you need depends on both your pool’s water volume and how far your current reading is from your target. A small above-ground pool needs a fraction of what a large inground pool needs to make the same change, which is why every dosing chart starts with gallons.
Free Chlorine (Sanitizer Level)
Free chlorine (FC) is what actually kills bacteria and algae in your pool. For routine maintenance, most pools are kept between 2–4 ppm. If your pool has turned green, cloudy, or has an algae bloom, you’ll typically shock it up to 10 ppm or higher (following CYA-based shock guidelines from the CDC or your test kit).
The calculator above uses the standard water-treatment dosing formula — ppm change × (gallons ÷ 1,000,000) × 8.34 — to find the pounds of active chlorine needed, then divides by your product’s percent-available chlorine to get an actual amount of liquid or granular product to add.
pH
Pool water pH should sit between 7.2 and 7.6. Below that range, water becomes corrosive to metal fittings and heaters and can irritate skin and eyes; above it, chlorine becomes far less effective at sanitizing. Soda ash (sodium carbonate) raises pH, while muriatic acid or dry acid lowers it.
Total Alkalinity
Total alkalinity (TA) acts as a buffer that keeps pH from swinging wildly every time you add chlorine or the pool gets rained on. The ideal range is 80–120 ppm. Baking soda (sodium bicarbonate) is the standard, inexpensive way to raise it.
Order of Operations
- Total Alkalinity first — it stabilizes pH so your next adjustments actually hold.
- pH second — correct pH before shocking, since chlorine works best in the right range.
- Chlorine last — sanitize once your water chemistry is balanced.
Always add chemicals separately, never mix them together before adding to the pool, and retest after a few hours of circulation before dosing again.
Frequently Asked Questions
How often should I test my pool water?
2–3 times per week during swim season, and daily during a heat wave, heavy rain, or heavy bather load.
Can I use this calculator for a hot tub or spa?
The same formulas apply, but hot tubs are small enough that even tiny dosing errors swing ppm readings fast — add half the suggested amount, retest, and adjust from there.
Why did my chlorine reading not change after dosing?
High chlorine demand (from algae, combined chlorine, or low stabilizer/CYA) can consume added chlorine before it registers on a test strip. Retest in a few hours, and consider a CYA test if this keeps happening.