GardenCalc
Soil volume, mulch quantity, plant spacing, fertilizer mixing, garden bed area, and bonsai wire gauge. Plan your garden from your phone.
Soil Volume Calculator
Calculate cubic feet and cubic yards of soil for raised beds, pots, and garden areas.
Mulch Calculator
Calculate how many cubic yards or bags of mulch you need for any area.
Plant Spacing Calculator
Calculate how many plants fit in a row or garden bed with even spacing.
Fertilizer Calculator
Calculate how much fertilizer to apply based on NPK ratio and target application rate.
Garden Bed Area Calculator
Calculate area for rectangular, circular, and L-shaped garden beds.
Bonsai Wire Gauge Calculator
Find the recommended copper or aluminum wire thickness for a branch by diameter.
About GardenCalc
GardenCalc helps gardeners and landscapers estimate materials before heading to the garden center. Every calculation runs in your browser — no data leaves your device.
Whether you're filling raised beds, mulching flower borders, spacing transplants, mixing fertilizer, or measuring irregular garden areas, these tools give you instant answers you can share via URL.
Soil volume for raised beds: volume = length × width × depth. A standard 4×8 foot raised bed at 12 inches deep needs 4 × 8 × 1 = 32 cubic feet = 32/27 = 1.19 cubic yards of soil. The Mel's Mix formula for raised bed growing is 1/3 compost, 1/3 peat moss or coco coir, 1/3 coarse vermiculite by volume — no native soil. This mix drains well, doesn't compact, and supports intensive square-foot planting.
Plant spacing and square-foot gardening: intensive spacing packs plants based on mature canopy size rather than row planting. Tomatoes: 1 per square foot (indeterminate, staked); lettuce: 4 per square foot; radishes: 16 per square foot; spinach: 9 per square foot; carrots: 16 per square foot; corn: 1 per square foot (plant in 4×4 block minimum for pollination). Spacing calculator takes mature plant diameter × mature plant diameter to find square feet per plant.
Fertilizer math: N-P-K numbers on bags are weight percentages. A 10-10-10 fertilizer is 10% nitrogen, 10% phosphorus (as P₂O₅), 10% potassium (as K₂O) by weight. To apply 1 lb of nitrogen per 1,000 sq ft from a 10-10-10 fertilizer: 1 lb N / 0.10 = 10 lbs of fertilizer needed per 1,000 sq ft. Vegetable gardens at peak production typically need 1–2 lbs of actual nitrogen per 1,000 sq ft per growing season.
Frost date and growing season: last spring frost and first fall frost dates define the growing season length and determine when to plant frost-sensitive crops. Days-to-maturity on seed packets assume soil temperature and conditions near the plant's optimum. To back-calculate first planting date: last frost date − days to maturity − 2 weeks for establishment = latest start date for outdoor transplanting of warm-season crops.