About Pool Sums

Pool Sums is a set of free calculators for the backyard: how many gallons the pool holds and what to add to it, what size heater, how much seed, sod and fertilizer the lawn needs, how many plants fit a bed, and how much soil fills it. Each one is built on a published rate or a standard formula, and each page shows the arithmetic rather than asking you to trust a number.

Where the numbers come from

Pool volume is geometry at 7.48 gallons per cubic foot, with the 0.785 oval and 0.45 kidney factors the equipment makers use. Salt is the 1 ppm = 1 mg/L definition applied to 8.34 lb gallons. Chlorine doses are the standard pool-store figures per ppm per 10,000 gallons for each product, with free-chlorine targets set as a share of cyanuric acid per the Trouble Free Pool chart. Heater sizing uses the 8.34 × gallons × ΔT heat-up formula and the 12 BTU per square foot per degree maintenance rule from Hayward and Raypak sizing guides. Seeding rates and annual nitrogen come from university extension services (Purdue, Penn State, Texas A&M). Sod pallets are 450 square feet, the common size. Raised-bed mixes are Mel Bartholomew's square-foot mix and the common 60/30/10 blend.

What this site doesn't do

It doesn't store what you enter, require an account, or override a product label. A chlorine dose is only as good as the test reading you gave it; fertilizer rates assume the bag's stated analysis; a heater size is a starting point for a quote. Pool chemicals are hazardous when mixed or stored wrongly, and the label's directions govern every dose here.

Corrections

If you are a pool professional, turf manager or extension agent and a rate, factor or dose here is out of date, email hello@poolsums.com. Sources are named on each page so a correction can be checked against them.