Gardening calculators
5 free tools
The backyard math that saves you a second trip to the store — pounds of grass seed, how much fertilizer to spread, how many plants fit a bed, cubic feet of soil, and gallons of water a week. Enter feet and inches, get numbers you can act on.
Turn a nitrogen target and the bag's N percent into pounds of product to spread.
Pounds of grass seed for a new lawn or an overseed, from your lawn size and rate.
How many plants fit a bed — rows, plants per row, and the total at your spacing.
Cubic feet and yards of soil to fill a raised bed, plus how many bags to buy.
Gallons of water your garden needs each week from its area and inches wanted.
Frequently asked questions
Are these calculators set up for US home gardens?
They are — everything runs in feet, inches, pounds, and gallons, sized for backyard lawns and beds rather than farm acreage. Seeding and fertilizer rates follow the per-1,000-square-feet convention you'll see on bags at the store.
Why do seed and fertilizer use rates per 1,000 sq ft?
That's the unit the industry prints on the bag, so matching it keeps you honest. Your lawn's area divided by 1,000, times the rate, gives the amount to buy without any guesswork or unit juggling.
How do inches of water become gallons?
One inch of water over a square foot is about 0.623 gallons. The watering tool multiplies your garden's area by the inches you want and by that factor, so an inch a week turns into a gallon count you can plan around.