Gardening Calculators
Companion Planting Calculator
Look up whether two garden crops are a documented good, bad, or neutral companion-planting pairing, with the traditional reasoning behind each rating.
Compost Calculator
Turn a garden bed's area and target compost depth into cubic feet and cubic yards needed, with guidance on topdressing versus new-bed preparation depths.
Drip Irrigation Flow Calculator
Calculate total system flow rate and water delivered by a drip irrigation system based on emitter count and run time.
Garden Bed Layout Calculator
Calculate how many plants fit in a garden bed using a simple grid layout based on bed dimensions and plant spacing.
Garden Fertilizer Calculator
Convert a target nitrogen application rate and a fertilizer's N-P-K percentage into the exact pounds of product needed for your garden bed or lawn area.
Garden Soil Calculator
Calculate the cubic feet and cubic yards of soil needed to fill a garden bed from its length, width, and depth, plus an estimated bag count for bagged soil.
Garden Watering Schedule Calculator
Convert the standard 1-inch-per-week watering guideline into exact gallons for your garden area, split across however many times a week you water.
Garden Yield Estimator
Estimate your total expected garden harvest based on number of plants and expected yield per plant.
Greenhouse Heating Requirement Calculator
Calculate the BTU/hour heater capacity needed to maintain your greenhouse's target temperature during cold weather.
Growing Season Length Calculator
Calculate your garden's frost-free growing season length from last spring frost and first fall frost dates.
Lawn Seed Calculator
Calculate how many pounds of grass seed you need based on lawn area and seed application rate.
Mulch Depth Calculator
Calculate the mulch volume needed for a garden area at a given depth, with guidance on the 2-4 inch range that avoids weed breakthrough or stem rot.
Plant Spacing Calculator
Calculate exactly how many plants fit a garden bed from its length, width, and spacing, with a grid layout and common crop spacing reference table.
Raised Bed Plant Capacity Calculator
Calculate how many plants your raised garden bed can hold based on bed dimensions in feet and required plant spacing.
Raised Bed Soil Calculator
Calculate total soil volume across multiple identical raised beds at once from bed dimensions, fill depth, and bed count, in cubic feet and cubic yards.
Seed Germination Rate Calculator
Calculate seed germination rate percentage from a test batch to assess seed quality before planting your full supply.
Seed Starting Date Calculator
Calculate the exact calendar date to start seeds indoors by counting back the recommended number of weeks from your area's average last frost date.
Soil pH Amendment Calculator
Calculate how much garden lime or elemental sulfur you need to shift your soil to a target pH level.
Tree Age Calculator
Estimate a standing tree's age from a trunk circumference or diameter measurement using published forestry growth factors for over 20 common species.
Vermicompost Worm Bin Calculator
Calculate how many worms and how much bin surface area you need to process a target amount of daily food scraps.
Growing Things on Purpose
A garden rewards planning more than most hobbies — the right soil mix, spacing, and watering schedule make the difference between a thriving bed and a struggling one. These ten calculators cover the practical math behind planning a garden.
Building a Compost Pile That Actually Breaks Down
- Start with roughly 25-30 parts carbon ("browns") to 1 part nitrogen ("greens") by weight. Browns are dry material like dead leaves, straw, and cardboard; greens are fresh material like grass clippings and vegetable scraps.
- Layer, don't just dump. Alternating browns and greens in layers helps microorganisms access both materials evenly rather than one dominating a section.
- Keep it about as damp as a wrung-out sponge. Too dry and decomposition stalls; too wet and the pile turns anaerobic and starts to smell.
- Turn the pile every 1-2 weeks. This reintroduces oxygen, which aerobic decomposition depends on to keep working efficiently rather than slowing to a crawl.
The Compost Calculator works out the ratio for your specific mix of materials, and the Garden Soil Calculator estimates how much finished compost or soil amendment a given bed actually needs.
Popular Gardening Calculators
- Plant Spacing Calculator — converts a bed's dimensions and a plant's mature size into how many plants actually fit.
- Garden Watering Schedule Calculator — estimates watering frequency from climate, soil type, and plant needs.
- Companion Planting Calculator — suggests compatible plant pairings based on traditional companion planting guidance.
Related: Landscaping Calculators for larger-scale yard projects, Agriculture Calculators for field-scale growing.