Chlorine & Shock Calculator

Enter your volume and readings; get the exact dose in ounces, pounds, or fluid ounces.

Chlorine & shock dose calculator

Enter your pool volume, your current free-chlorine reading, and your target. The result is the amount of product to add. Default target is 10 ppm (a routine shock); day-to-day free chlorine should sit in the 1–3 ppm range.

You need to add

Cal-hypo shock (Calcium hypochlorite, 65%)
1.28 lb
= 20.5 oz (1.28 lb) by weight
Raising free chlorine by
10 ppm
0 → 10 ppm in 10,000 gal
Show the math

Raising 1 ppm in 10,000 gal takes 37.854 g of pure available chlorine (1 mg/L × 37,854 L).

Pure chlorine needed = 37.854 × 10 ppm × 10,000 / 10,000 = 378.5 g.

Cal-hypo shock (Calcium hypochlorite, 65%) is 65% available chlorine, so product needed = 378.5 g / 0.65 = 20.5 oz.

Most common bagged pool shock. Raises calcium hardness slightly.

Estimate only. Broadcast dissolved product with the pump running, re-test after ~4 hours, and never mix chlorine products together. Trichlor and dichlor also raise cyanuric acid over time.

Which chlorine product should I use?

  • Cal-hypo shock (65–73%): the standard bagged shock. Fast, strong, adds a little calcium.
  • Dichlor (56%): stabilized granules — convenient but adds cyanuric acid, so watch CYA over a season.
  • Trichlor tabs (90%): slow-dissolve 3″ tabs for a floater or feeder; also acidic and adds CYA.
  • Liquid chlorine (10–12.5%): no CYA and no calcium — ideal for regular dosing and for high-CYA pools.

Shocking vs. routine dosing

For routine sanitation, keep free chlorine in the 1–3 ppm range. To shock (breakpoint chlorination), raise free chlorine to about 10 ppm — higher if you are clearing algae. Add dissolved product with the pump running and re-test after a few hours before swimming.

Don’t know your volume? Use the pool volume calculator first, or jump to a chlorine dose for a specific pool size.

Chlorine, shock & test supplies

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HTH / In The Swim / DryTec
Pool Shock (Cal-Hypo / Calcium Hypochlorite)

Granular cal-hypo shock for breakpoint chlorination. Pairs with the shock dosing calculator.

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Clorox / In The Swim / Rx Clear
3-inch Chlorine Tablets (Trichlor)

Slow-dissolve stabilized 3" tabs for a floater or inline feeder. Adds cyanuric acid over time.

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AquaChek / JNW
7-in-1 Pool & Spa Test Strips

Fast strips for free chlorine, pH, total alkalinity, cyanuric acid and hardness — the inputs every calculator here needs.

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