Gardening & Lawn Tools

Free gardening, lawn and outdoor calculators that run entirely in your browser — plant and tree spacing, grass seed, fertilizer NPK, raised-bed and pond volume, sod, sprinkler and drip run-time, grow-light DLI, seed-starting dates, growing degree days, soil pH/lime, rainwater harvesting and hydroponic nutrients. Nothing is uploaded.

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Plant Spacing Calculator

Find how many plants fit a garden bed from in-row and between-row spacing, for square or triangular layouts.

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Grass Seed Calculator

Calculate pounds of grass seed and bags needed by lawn area, grass type and new-lawn or overseeding rate.

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Fertilizer / NPK Calculator

Work out pounds of fertilizer for a target nitrogen rate and the N, P and K actually applied from the label numbers.

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Grow Light DLI Calculator

Convert PPFD and photoperiod to Daily Light Integral (DLI), or solve the PPFD or hours needed for a target DLI.

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Seed Starting Date Calculator

Find when to sow seeds indoors and transplant, counted from your last spring frost date, per crop.

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Sprinkler & Drip Run-Time Calculator

Calculate how long to run a sprinkler or drip system to apply a target water depth, in minutes.

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Raised Bed Soil Calculator

Estimate soil volume in cubic feet and yards for raised beds, split by mix, with bag counts.

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Tree Spacing / Trees-Per-Acre Calculator

Find trees per acre from row and in-row spacing, or how many trees fit a plot of a given length and width.

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Sod Calculator

Estimate sod for a lawn: add multiple areas, include a waste allowance, and get rolls and pallets to order.

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Hydroponic Nutrient & EC/PPM Calculator

Convert EC to PPM on the 500 or 700 scale, and find the mL of nutrient to raise a reservoir to a target EC.

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Pond Volume, Liner & Fish Calculator

Calculate pond volume in gallons and liters, the liner size needed, and safe koi and goldfish stocking counts.

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Rainwater Harvesting Calculator

Estimate rainwater collected from a roof for a given rainfall, plus the 55-gallon barrels needed to store it.

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Lawn Lime & Soil pH Calculator

Find how much lime to raise soil pH, or sulfur to lower it, by soil texture and area, with a per-1000 ft² rate.

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Growing Degree Days Calculator

Accumulate growing degree days from daily high/low temperatures with a base temperature and optional upper cap.

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Vapor Pressure Deficit (VPD) Calculator

Calculate vapor pressure deficit (VPD) in kPa from temperature and humidity for grow rooms and greenhouses, with grow-stage target zones.

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