Plan Your Garden With Real Numbers
Use simple gardening calculators to estimate plant spacing, seed quantities, watering needs, soil, mulch, and other garden inputs before you buy or plant.
Most Popular Garden Calculators
Plug in your measurements and get a number you can plant or shop with.
Seed Calculator
Work out how many seeds to buy and sow from your bed size, spacing, germination rate, and seeds per hole.
Calculate Seeds →Plant Spacing Calculator
Turn bed dimensions and a crop spacing into rows, plants per row, and a total plant count — square grid or offset.
Calculate Spacing →Soil Calculator
Calculate how many cubic feet or cubic yards of soil you need for raised beds and garden containers.
Calculate Soil →Mulch Calculator
Estimate cubic feet, cubic yards, and bags of mulch for any bed from its size and your chosen depth.
Calculate Mulch →Watering Calculator
Get a weekly watering frequency, gallons per week for your bed, and optional drip run times.
Calculate Watering →Recommended Gear for Your Garden Plan
Once you have your numbers, these guides help you pick supplies that fit them.
Raised beds and garden structures
Pick a bed size that divides cleanly into rows, then work out how much soil it takes to fill.
Seed-starting and planting supplies
Size trays, lights, and heat mats to the number of seeds you actually need to start.
Drip irrigation, timers, hoses, and moisture tools
Match emitters and run times to your weekly gallons, and check the soil before you water.
Built for Practical Garden Planning
Calculate
Estimate what your garden needs: seeds, plants, soil, mulch, and water.
Plan
Turn measurements into a planting plan with spacing and layouts that fit your beds.
Plant
Buy and plant with fewer guesses, and fewer second trips to the garden center.
Latest Articles
Fresh guides on spacing, seeds, and watering — all grounded in the numbers.
An Atmospheric River May Hit the West Coast Next Week: The Runoff and Drainage Math for Your Garden
Early forecasts show a month of rain in days for parts of California and heavier totals in the Northwest. How much water your roof sends toward your beds, how long your soil needs to drain it, and how much to raise a wet bed.
Read more → Garden PlanningNeil Sperry Says Chill Tulips 45 Days Before a Late-December Planting: The Calendar and Bulb-Count Math
Texas horticulturist Neil Sperry says tulips and Dutch hyacinths need at least 45 days at 45°F before a late-December planting. How to count back to your start date and how many bulbs a bed takes.
Read more → Garden PlanningIllinois Extension Says Put Your Leaves to Work: The Bag, Depth, and Compost-Ratio Math
Illinois Extension wants fallen leaves mowed in, mulched, composted, or used as insulation instead of bagged. How many bags each job takes, and how to balance a leaf-heavy compost pile.
Read more →Free Guide: “Garden Math Made Simple”
A 20-page PDF of the formulas behind every calculator on this site — spacing, seed counts, soil, mulch, and watering — with reference tables and printable planning worksheets.
- Garden layout planning with simple geometry
- Plant spacing and seed-count formulas
- Soil, mulch, and watering tables in cubic feet, bags, and gallons
“Garden Math Made Simple”
20 pages · PDF · free