Gardening Calculators
Plan your garden with confidence using our free gardening calculators. Whether you need to figure out plant spacing for a vegetable bed, calculate how much soil or mulch to buy, plan your seed starting schedule around your frost date, or estimate compost and fertilizer needs, these tools do the math so you can focus on growing. All calculators are free, instant, and work on any device.
Planting & Layout
Spacing, scheduling, and bed planning tools.
Plant Spacing Calculator
Calculate how many plants fit in your garden bed with proper spacing.
Seed Starting Calculator
Find when to start seeds indoors based on your last frost date.
Raised Bed Calculator
Calculate soil volume, lumber, and cost for raised garden beds.
Soil, Mulch & Compost
Volume and coverage calculators for garden materials.
Soil Calculator
Calculate how much soil you need in cubic feet or cubic yards.
Mulch Calculator
Estimate mulch volume and bags needed for your beds.
Compost Calculator
Calculate the right green-to-brown ratio for your compost pile.
Watering & Fertilizing
Keep your garden healthy with the right inputs.
Frequently Asked Questions
How do I calculate plant spacing for my garden?
Plant spacing depends on the mature size of each plant. Divide your garden bed dimensions by the recommended spacing distance to find how many plants fit in each row and column. For example, if a plant needs 12 inches of spacing in a 4-foot by 8-foot bed, you can fit 4 plants across and 8 plants deep for 32 total plants. Our calculator handles square foot, row, and hexagonal spacing methods.
How much soil do I need for a raised bed?
Calculate the volume of your raised bed by multiplying length x width x depth. A 4x8 foot bed that is 12 inches deep needs 32 cubic feet (about 1.2 cubic yards) of soil. Most garden centers sell soil by the cubic foot or cubic yard. Our raised bed calculator handles rectangular, L-shaped, and circular beds and estimates cost based on your local soil price.
When should I start seeds indoors?
Seed starting dates depend on your last frost date and the number of weeks each plant needs indoors before transplanting. Tomatoes typically need 6-8 weeks, peppers need 8-10 weeks, and lettuce needs 4-6 weeks. Our seed starting calculator takes your last frost date and shows a custom planting schedule for dozens of common vegetables, herbs, and flowers.
How much mulch do I need?
Mulch is typically applied 2-4 inches deep. Measure the area of your beds in square feet, multiply by the desired depth in feet, and you get the volume in cubic feet. Divide by 27 to convert to cubic yards. A 100 square foot bed with 3 inches of mulch needs about 25 cubic feet or just under 1 cubic yard. Our calculator estimates both volume and number of bags needed.