Garden calculators
10 browser-based garden calculators and utilities. Every formula runs locally - no upload, no sign-up, no tracking of the numbers you type.
All garden tools
10 tools, each runs locally in your browser. Click any card to open it.
Pounds of browns and greens to fill a bin at the ideal C:N ratio.
Compost C:N Ratio Calculator takes numbers, ranges, parameters and returns the matching compost c:n ratio result. Runs…
Irrigation Water Budget Calculator computes internal rate of return from cash flow stream (initial outflow then inflow…
Lawn Fertilizer Calculator takes project parameters or constraints and returns the matching lawn fertilizer result. Ru…
Compare buying a mower vs hiring a service over 5 years.
Lawn Mulch Thickness Calculator takes length, area, volume, material rate and returns the matching lawn mulch thicknes…
1 inch/week including rain. Deep + infrequent > shallow + daily.
Mulch Calculator takes length, area, volume, material rate and returns the matching mulch result. Runs entirely in you…
L × W × depth = cubic feet → cubic yards → bags.
Seed Spacing Calculator takes project parameters or constraints and returns the matching seed spacing result. Runs ent…
About garden
Garden calculators cover the basic sizing math home gardeners and small-farm operators need: soil amount by bed dimensions and depth, mulch and compost in cubic yards, plant spacing by mature width, lawn seed by square footage, NPK fertilizer ratios for vegetables / lawns / shrubs, frost-date planning by USDA zone, watering schedules by plant type and climate, and raised-bed soil mix proportions.
Use these tools when filling a new 4×8×12 inch raised bed (about 1 cu yd of mix), planning tomato spacing at 24-36 in, sizing a 1,500 sq ft lawn for 5 lb of cool-season seed, dosing 10-10-10 fertilizer per the application rate on the bag, or computing first/last frost dates for transplanting based on your zone.
Sources: USDA Plant Hardiness Zone Map, NRCS soil amendment recommendations, university extension publications (Cornell, UF/IFAS, Oregon State). Defaults to US units; toggle metric per project.
Common use cases
Real scenarios where the garden calculators in this category earn their keep.
Raised bed soil volume
Length × width × depth in feet, divided by 27 for cubic yards. The tool recommends a mix (60% topsoil / 30% compost / 10% peat or coir typical).
Mulch by square footage
Coverage at 3 inches deep = 108 sq ft per cubic yard. The mulch calculator outputs cubic yards and bag count for any bed area.
Plant spacing for tomatoes
24-36 inches between determinate tomatoes; 36-48 for indeterminate trained on stakes; 4 ft if caged. The spacing tool returns plant count per bed dimension.
Lawn seed for over-seeding
Cool-season blends at 3-5 lb per 1,000 sq ft over-seed, 6-8 lb for new lawn. The seed calculator picks the rate by purpose.
Frost dates by zone
Average first and last frost dates for any USDA hardiness zone. The tool returns transplant windows for warm-season vegetables.
Key terms
Glossary for the formulas and conventions these tools use.
- USDA zone
- USDA Plant Hardiness Zone. Numbered 1-13 by average annual minimum temperature, used to pick perennials and time annuals.
- NPK
- Nitrogen, Phosphorus, Potassium. Three numbers on every fertilizer bag (e.g. 10-10-10). N for foliage, P for roots and flowers, K for overall vigor.
- Cubic yard
- 27 cubic feet. Standard unit for bulk soil, compost, mulch, and gravel delivery.
- Cool-season vs warm-season grass
- Cool: fescue, ryegrass, bluegrass; grows in spring/fall, dormant in summer. Warm: bermuda, zoysia, St. Augustine; opposite cycle.
- Drip irrigation GPH
- Gallons Per Hour. Standard emitters: 0.5, 1, 2 GPH. Used to size watering runtime per plant or row.
- Mulch depth
- 2-4 inches typical. Less = won't suppress weeds. More = can suffocate roots and hold too much moisture against stems.
- First / last frost date
- Average dates of the first 32°F night in fall and last in spring. Drives transplant timing for warm-season crops.
Frequently asked questions
Short answers to the most common garden questions.