Backyard Calculators With the Working Shown
Free backyard calculators with the working shown: pool volume, salt/chlorine doses, heater size, grass seed and sod, fertilizer, plant spacing, and soil.
Most backyard calculators give you a number and no reason to believe it. Every tool here uses a published rate or a standard formula, shows the arithmetic, and says what to buy -- bags of salt, pallets of sod, the heater on the shelf that covers the load.
Pool covers volume, salt, chlorine and heater sizing. Lawn covers seed, sod and fertilizer. Garden covers plant counts and raised-bed soil.
Pool
How many gallons (and litres) your pool holds from its shape, dimensions and shallow and deep depths, with the surface area, fill cost and fill time.
Salt to addPounds and 40 lb bags of salt to bring your pool to the 3,200 ppm most salt chlorine generators want, and what each bag moves the reading by.
Chlorine & shock doseHow much liquid chlorine, cal-hypo, dichlor or trichlor to raise free chlorine to your target or shock level, from your cyanuric acid reading.
Shock doseHow much shock (cal-hypo, dichlor, trichlor or liquid chlorine) to add to reach SLAM level from your cyanuric acid reading, in pounds or gallons.
Heater BTUsThe gas heater or heat pump size in BTU/h to warm your pool by a set number of degrees in a set time, and hold temperature against your climate.
Pump GPMThe flow rate (GPM) and pump size to turn your whole pool over in 8-10 hours, from your gallons and desired turnover time.
Lawn
Pounds of grass seed for a new lawn or overseeding from your square footage and grass type, using university extension seeding rates, in bags.
Fertilizer by N ratePounds of fertilizer to apply from your lawn area, the bag N-P-K, and nitrogen rate per 1,000 sq ft, with an annual nitrogen plan by grass type.
Sod pallets & rollsPallets and rolls of sod for your lawn area with 5% waste, and the cost at your supplier's pallet price.
Garden
How many plants fit a bed or border at a given spacing, in square, triangular or row layouts, with a table of common vegetable and groundcover spacings.
Raised bed soilCubic feet, cubic yards and bags of soil to fill a raised bed from its dimensions, split into compost, peat and other components for the mix you choose.
Frequently Asked Questions
Where do the numbers come from?
Each calculator names its source on the page: geometry at 7.48 gallons per cubic foot for pool volume, the standard pool-store chlorine and salt dosing figures, Hayward and Raypak heater sizing rules, university extension seeding and nitrogen rates, and the common raised-bed mixes. Nothing here is invented; the arithmetic is shown so you can check it.
Do these replace the product label?
No. The label governs any chemical or fertilizer dose, and a pool-store water test or a soil test is the real basis for a treatment. The calculators tell you what the standard rates imply for your numbers so you can buy the right amount and understand the label.
Do I need an account, and is anything saved?
No account, nothing saved. Every calculation runs in your browser and nothing you type is sent anywhere.