Professional tools for chlorine dosing, water balance, and LSI calculation
PoolDose is a free, independent set of calculators for residential pool and hot tub owners who want to dose chemicals accurately instead of guessing. Below is the practical methodology behind every tool here, written so you can balance your own water with confidence and understand exactly what each number means before you add anything.
Healthy pool water is a balance of a handful of linked measurements, and the order you balance them in matters. Free Chlorine (FC) is the active sanitizer that kills bacteria and algae; the CDC's Healthy Swimming guidance recommends keeping at least 1 ppm FC in pools at all times, and most owners hold 3–5 ppm for a comfortable margin. Combined Chlorine (CC) is the used-up chlorine bound to contaminants — when it climbs above about 0.5 ppm you get the harsh chloramine smell and stinging eyes, which is a sign you need to shock, not add more swimmers. pH (ideal 7.2–7.6) controls how effective your chlorine is and how comfortable the water feels. Total Alkalinity (TA, typically 80–120 ppm) buffers pH so it stops bouncing around. Cyanuric Acid (CYA, usually 30–50 ppm) is a stabilizer that shields chlorine from sunlight. Each of these calculators isolates one of these parameters so you can correct it without disturbing the others.
Not all chlorine is the same strength, and picking the wrong product is the most common dosing mistake we see. Liquid chlorine (sodium hypochlorite) is typically 10–12.5% available chlorine and adds nothing else to the water. Cal-hypo (calcium hypochlorite) granules are usually 65–73% and also raise calcium hardness, which matters in already-hard water. Dichlor is roughly 56% available chlorine but also adds cyanuric acid with every dose, so it slowly over-stabilizes a pool if used as your everyday sanitizer. Because each product carries a different amount of usable chlorine per ounce or gram, the chlorine and shock calculators let you pick your exact product so the recommended amount reflects what is actually in your container — always confirm the percentage printed on the label, since strengths vary by brand.
Every dosing tool here follows the same transparent formula: dose = pool volume × (target level − current level) × a product-specific factor. That is why an accurate volume is the foundation of good chemistry — a pool that is off by 20% in gallons will be off by 20% in every chemical you add. As a worked example, raising Free Chlorine by 1 ppm in a 10,000-gallon pool takes roughly 10.7 fluid ounces of 12.5% liquid chlorine, or about 2 ounces by weight of 65% cal-hypo. We deliberately show the method rather than hiding it behind a black box, because understanding the relationship between volume, the gap you are closing, and product strength is what lets you sanity-check any result before you pour it in.
Water chemistry is connected, so the tools are designed to be used as a sequence rather than in isolation. Start with the Pool Volume calculator, since every other dose depends on it. Next balance Total Alkalinity, then pH, because a stable alkalinity keeps pH from drifting after you adjust it. Confirm your CYA is in range so your chlorine is protected from the sun, then use the Chlorine calculator for everyday sanitizing or the Shock calculator when Combined Chlorine has built up. The LSI calculator ties the picture together by checking whether your overall balance is corrosive or scale-forming. Working through them in this order — the same workflow a service technician follows — prevents the frustrating cycle of fixing one number only to knock another out of range.
These calculators are built for everyday residential pool and spa owners, and they are estimates to guide your dosing, never a replacement for a reliable test kit. Always test your water with fresh reagents or strips the same day you dose, because chlorine and pH change hour to hour with sunlight, temperature, and bather load. Real pools have variables a calculator cannot see — splash-out, rain dilution, heavy debris, an aging surface, or an inaccurate volume estimate — so treat every result as a well-grounded starting point and retest a few hours after dosing. Never mix chlorine products together or combine any chlorine with acid, as this can release toxic gas. We built PoolDose around transparent, free pool chemistry methodology rather than selling products, and nothing here is a substitute for professional advice when a problem persists or a chemical situation feels unsafe.