Pool Chemical Dosage Calculator
Calculate the exact amount of chlorine needed to raise your pool to a safe target level. Perfect for pool owners performing routine shock treatments or correcting low sanitizer readings.
About this calculator
Chlorine dosage is calculated from the deficit between your current and desired chlorine levels scaled to pool volume. The formula is: dosage (kg) = (targetChlorine − currentChlorine) × poolVolume × 0.01, where chlorine levels are in parts per million (ppm) and pool volume is in cubic meters. One ppm equals 1 mg per liter, or 1 g per cubic meter. The factor 0.01 converts ppm × m³ into kilograms of active chlorine required, accounting for the fact that most commercial chlorine products are not 100% pure — you may need to adjust upward based on your product's active chlorine percentage (typically 65–99%). Ideal pool chlorine levels are 1–3 ppm for free chlorine; shocking typically targets 5–10 ppm temporarily.
How to use
Example: your pool volume is 50 m³, current chlorine reads 0.5 ppm, and you want to reach 2.0 ppm. Step 1 — find the deficit: 2.0 − 0.5 = 1.5 ppm. Step 2 — apply formula: 1.5 × 50 × 0.01 = 0.75 kg of active chlorine needed. Step 3 — if your granular chlorine product is 70% active chlorine, divide: 0.75 / 0.70 ≈ 1.07 kg of product to add. Always pre-dissolve granular chlorine in a bucket of water before adding to the pool.
Frequently asked questions
What is the ideal chlorine level for a swimming pool and why does it matter?
The recommended free chlorine range for most pools is 1–3 ppm (parts per million). Below 1 ppm, chlorine cannot reliably kill bacteria and algae, creating health risks for swimmers. Above 3 ppm, the water may irritate eyes and skin, bleach swimwear, and produce a strong chemical smell. During shock treatments, levels are temporarily raised to 5–10 ppm to eliminate algae blooms or combined chloramines, then allowed to drop back to the normal range before swimming resumes.
How does pool volume affect how much chlorine I need to add?
Chlorine dosage scales directly with pool volume because you're trying to achieve a target concentration throughout the entire body of water. Doubling the pool volume doubles the kilograms of chlorine required to achieve the same ppm increase. This is why accurate volume calculation is essential — a 10% volume underestimate leads to a 10% underdose, potentially leaving the pool under-sanitized. Always measure your pool dimensions carefully and use the average depth for pools with sloped floors.
Why does my chlorine level drop so quickly after adding it to the pool?
Chlorine is consumed by several processes: it kills bacteria and oxidizes organic matter (sunscreen, sweat, urine), it reacts with ammonia compounds to form chloramines, and UV sunlight breaks it down rapidly — outdoor pools can lose 50–90% of free chlorine within a few hours of direct sun exposure. Cyanuric acid (stabilizer) acts as a sunscreen for chlorine, significantly slowing UV degradation. Maintaining a cyanuric acid level of 30–50 ppm in outdoor pools dramatically reduces chlorine consumption and dosing frequency.