For most backyard pools, the usual guideline is:

  • Use one standard 3-inch chlorine tablet for every 5,000 gallons of pool water per week.

So for common pool sizes, that works out roughly as:

html

<table>
  <tr><th>Pool size (gallons)</th><th>Typical 3&quot; tablets per week</th></tr>
  <tr><td>5,000</td><td>1 tablet</td></tr>
  <tr><td>10,000</td><td>2 tablets</td></tr>
  <tr><td>15,000</td><td>3 tablets</td></tr>
  <tr><td>20,000</td><td>4 tablets</td></tr>
  <tr><td>25,000</td><td>5 tablets</td></tr>
</table>

Quick Scoop

  • A single 3-inch tablet can sanitize up to about 5,000 gallons of water.
  • Most people end up using 2–4 tablets per week to keep chlorine around 1–3 ppm in a typical residential pool.
  • Always round your pool volume up to the nearest 5,000 gallons when deciding how many tablets to use (better to under-dose slightly and re-test than to heavily over-chlorinate).
  • Tablets usually dissolve over 3–5 days , so you’ll often add them once or twice a week depending on swimmer load, sun, and rain.

How to decide for your pool

  1. Estimate your pool volume in gallons (length × width × average depth × 7.5 for rectangular pools is a common formula).
  1. Divide that number by 5,000 to get a starting number of 3-inch tablets per week.
  2. Place tablets in a floater, in-line/off-line chlorinator, or skimmer (if manufacturer allows), never scattered directly on the liner or surface to avoid bleaching and damage.
  1. Test chlorine regularly and adjust tablet count so free chlorine stays around 1–3 ppm.

A quick example story

Imagine you’ve got a 20,000-gallon in-ground pool heading into a hot, sunny weekend. You drop four 3-inch tablets into your chlorinator at the start of the week. After a few days of heavy swimming and sunlight, you test and see chlorine drifting toward the low end of the ideal range, so you top up with another tablet or two instead of shocking right away. That kind of small, regular adjustment is typically how people keep the water clear without wasting chemicals or irritating swimmers.

Bottom line: start with about 1 tablet per 5,000 gallons per week , then fine-tune based on test-kit readings and the instructions on your specific tablet brand.

TL;DR:
For “how many chlorine tablets for pool,” a good starting point is 1× 3-inch tablet per 5,000 gallons of water per week , then adjust up or down after testing your chlorine level. Always follow your tablet manufacturer’s directions and your test kit over any generic rule.

Information gathered from public forums or data available on the internet and portrayed here.