Grow a Garden Calculator
Plan your garden bed, calculate how many plants you can fit, estimate the soil you need to buy, and predict your vegetable yield. Designed for raised beds, square foot gardening, and traditional row gardens.
Garden Dimensions
Planting Details
Enter your garden dimensions and plant type to see your plan…
Common Vegetable Spacing & Yield Guide
Yields are estimates for a 10-foot row under average conditions. Actual yields depend on sunlight, water, and soil quality.
| Vegetable | Spacing (inches) | Sq Ft Per Plant | Plants / 10ft Row | Est. Yield (10ft row) |
|---|---|---|---|---|
| Tomatoes | 24″ | 2.0 | 5 | 20 – 30 lbs |
| Peppers | 18″ | 1.5 | 8 | 10 – 15 lbs |
| Lettuce | 6″ | 0.25 | 20 | 3 – 5 lbs |
| Carrots | 3″ | 0.0625 | 40 | 10 – 15 lbs |
| Corn | 12″ | 1.0 | 10 | 15 – 20 ears |
| Bush Beans | 6″ | 0.25 | 20 | 3 – 5 lbs |
| Squash | 36″ | 9.0 | 3 | 20 – 40 lbs |
| Cucumbers | 12″ | 0.5 | 10 | 10 – 15 lbs |
| Onions | 4″ | 0.11 | 30 | 15 – 20 lbs |
| Potatoes | 12″ | 1.0 | 10 | 20 – 30 lbs |
| Beets | 6″ | 0.25 | 20 | 10 – 15 lbs |
| Eggplant | 18″ | 1.5 | 8 | 8 – 12 lbs |
Understanding square foot spacing
Plants need space for their roots to spread and their leaves to get sunlight. A tomato plant might only have a stem that is 2 inches wide, but its roots and leaf canopy require a 24×24 inch area (4 square feet). If you crowd plants too closely, they will compete for water and nutrients, leading to smaller harvests and increased disease.
Soil volume matters in raised beds
One of the biggest mistakes new gardeners make is underestimating how much soil it takes to fill a raised bed. A standard 4×8 foot raised bed that is 10 inches deep requires exactly 26.6 cubic feet of soil, which is almost 1 cubic yard or roughly 18 standard 1.5 cubic foot bags from the garden center. Buying bagged soil for large beds gets expensive quickly, so look into bulk soil delivery for beds over 6 inches deep.
Seed math and succession planting
Never plant exactly the number of seeds you need. If a seed packet has 80% germination and you need 20 plants, you should plant at least 25 seeds to account for the ones that will not sprout. For crops like lettuce and radishes that mature quickly, plant a small batch every 2 weeks (succession planting) so you have a continuous harvest all summer instead of everything being ready at once.
Watering requirements
Vegetable gardens typically need about 1 to 1.5 inches of water per week. In a 32 square foot garden (4×8), that equals roughly 20 to 30 gallons of water per week. During hot summer weeks, this can double. Mulching heavily with straw or wood chips cuts evaporation significantly and can reduce your watering needs by up to 50%.
Sunlight is non-negotiable
Fruiting vegetables like tomatoes, peppers, squash, and eggplant need a minimum of 6 to 8 hours of direct sunlight per day. Leafy greens and root vegetables can tolerate partial shade (4 to 6 hours). No amount of fertilizer or watering can compensate for a garden placed in too much shade. Observe your yard throughout the day before choosing your garden location.
What is a Grow a Garden Calculator?
A grow a garden calculator is a planning tool that helps you figure out how many plants will fit in your available space, how much soil you need to buy, and how many seeds to sow. It takes the guesswork out of garden planning by applying standard horticultural spacing rules to your exact garden dimensions.
Why planning ahead saves money
Without a plan, gardeners often buy too many seed packets, over-purchase bagged soil, or crowd too many plants into a small space. Crowded plants produce smaller yields and are more susceptible to pests and disease. This calculator helps you buy exactly what you need, reducing waste and increasing your chances of a successful harvest.
How the plant calculation works
The calculator divides your total garden area by the square footage required per plant. For example, if your garden is 32 square feet and each tomato plant needs 2 square feet, the calculator determines you can fit 16 plants. It then factors in germination rates to tell you exactly how many seeds to start indoors or direct sow.
How the soil calculation works
Soil volume is calculated by multiplying the garden area by the soil depth. The calculator converts this from cubic feet to cubic yards (the standard unit for bulk soil delivery) and to the number of standard 1.5 cubic foot bags (the most common bag size at hardware stores). This lets you instantly compare the cost of bulk delivery versus buying individual bags.
Who this calculator is for
This tool is for backyard gardeners, homesteaders, community garden organizers, and anyone starting a vegetable garden for the first time. It is especially useful for raised bed builders who need to know exactly how much soil to order, and for seed starters who want to avoid wasting expensive seed packets. The mobile-friendly layout makes it easy to use right in the garden center aisle while shopping for supplies.