Square Foot Gardening Calculator

This square foot gardening calculator shows how many plants of a crop fit in a given number of one-foot squares, and how many squares your bed has in total. Pick a crop, enter how many squares you want to give it, and enter your bed size. The calculator applies the standard square foot spacing for that crop, tells you how far apart to place plants within each square, and shows how many squares remain for other crops. For large crops such as zucchini and winter squash, it shows how many squares one plant needs.

What is square foot gardening?

Square foot gardening is an intensive planting method popularized by Mel Bartholomew in the late 1970s and 1980s. Instead of planting in long rows with paths between them, you grow in compact beds, usually 4 feet wide, divided into a grid of one-foot squares. Each square holds a set number of plants based on their size: 1, 4, 9 or 16 per square for most crops. Large sprawling plants take more than one square.

The method suits raised beds, small yards and beginners. Because every square is planned, it is easy to see exactly what goes where, to plant only as much as you need, and to replant a single square as soon as its crop is harvested. Compared with traditional rows, a square foot garden can produce a similar harvest from a fraction of the space, with less weeding and watering.

How to use the square foot gardening calculator

1. Choose a crop. The list shows each crop’s square foot rule, taken from our plant database.
2. Enter the squares for that crop. For example, 4 squares of carrots or 2 squares of tomatoes.
3. Enter your bed size in feet. A 4-by-4 bed has 16 squares, and a 4-by-8 bed has 32.
4. Read the result. The headline is the number of plants for the squares you chose. The table shows the spacing within each square and the squares left over.

Repeat for each crop you plan to grow and subtract the squares as you go, until the bed is full.

The square foot spacing rule

The number of plants per square comes from the crop’s normal spacing. Divide 12 inches by the spacing and square the result.

Plants per square = (12 ÷ spacing in inches)²

• 12-inch spacing: 1 plant per square. Peppers, basil, broccoli, cabbage, potatoes, and a single staked tomato.
• 6-inch spacing: 4 per square, in a 2-by-2 grid. Leaf lettuce, chard, parsley, garlic, cilantro.
• 4-inch spacing: 9 per square, in a 3-by-3 grid. Spinach, beets, onions, bush beans.
• 3-inch spacing: 16 per square, in a 4-by-4 grid. Carrots, radishes.

A few climbing crops are planted along a trellis at the back of the bed, so they get a different count. Peas and pole beans are commonly grown at around 8 per square in two short rows, and trellised cucumbers at about 2 per square.

To mark the positions, imagine dividing each square into a smaller grid. For 4 per square, place one plant in the center of each quarter, about 3 inches from the edges and 6 inches apart. For 9 per square, use a 3-by-3 grid with plants 4 inches apart. For 16, use a 4-by-4 grid 3 inches apart. Poking holes with a finger at each position before sowing makes it easy to be accurate.

Square foot chart for common crops

Varieties differ. A compact patio tomato or a bush zucchini needs less space than a vigorous heirloom or a vining squash. When a seed packet gives a spacing for the exact variety, use the formula above with that figure.

Worked example: carrots

Four squares of carrots at 16 per square hold 64 carrots. Planted in a 4-by-8-foot bed, they leave 28 of the bed’s 32 squares for other crops. The calculator shows a spacing of 3 inches within each square.

Worked example: zucchini

Zucchini is typically given a 3-by-3 block of squares, which is 9 squares for one plant. If you give it only 4 squares, the calculator returns zero plants and tells you it needs 9. Bush varieties trained against a stake and pruned regularly can sometimes be grown in less space, but expect lower yields and more disease pressure.

Planning a 4 by 8 square foot garden

A 4-by-8-foot bed gives you 32 squares, enough for a surprisingly varied garden. Here is one way a first-season bed might be planned, mixing quick crops with longer ones:

• Back row (8 squares along a trellis): 2 tomato squares, 2 cucumber squares, 4 squares of pole beans or peas.
• Middle rows (16 squares): 2 peppers, 2 basil, 2 broccoli or kale, 4 lettuce, 2 chard, 2 bush beans, 2 onions.
• Front row (8 squares): 3 carrots, 2 beets, 2 radishes, 1 parsley.

Put tall and trellised crops on the north side of the bed, so they do not shade the shorter crops. In the Northern Hemisphere, that keeps the low crops in full sun through the day.

Building and filling the bed

Square foot beds are traditionally 4 feet wide so you can reach the middle from either side, and 6 to 12 inches deep. Many gardeners use 4-by-4 or 4-by-8 beds made from untreated lumber, with a lattice of thin strips or string marking the squares.

The original method calls for a soilless mix of equal parts compost, peat moss or coco coir, and coarse vermiculite. It is light, holds water well and is easy to plant, though it costs more than soil-based mixes. Many gardeners now use a blend of topsoil, compost and an aerating ingredient instead. The raised bed soil calculator works out the volume of either mix for your bed.

Six inches of good mix is enough for many shallow-rooted crops, especially if the bed sits on loosened ground that roots can grow into. For deep-rooted crops such as tomatoes and long carrots, or for beds on hard surfaces, 12 inches or more is better.

Replanting squares through the season

One of the best features of square foot gardening is that each square is independent. When you harvest a square of radishes or lettuce, add a trowel of compost and replant it straight away with something else. This keeps the bed productive all season with very little effort.

• Spring to summer: follow early lettuce, spinach or radishes with bush beans, basil or a pepper plant.
• Summer to fall: after early beans or garlic, sow fall carrots, beets, kale or lettuce.
• Rotate crops: avoid planting the same crop family in the same square year after year, to reduce soil-borne pests and diseases.

The days-to-maturity column in the plant database helps you judge whether a replacement crop has time to finish before frost.

Square foot gardening versus rows

Row gardening leaves wide paths between every row so you can walk and cultivate, which means much of the garden is path rather than plants. Square foot gardening concentrates plants into beds and keeps paths outside them. The result is a smaller garden that needs less soil, compost, water and weeding for a similar harvest.

Rows still have advantages for large plantings of a single crop, such as a big patch of sweet corn or potatoes, and for gardeners using a tiller. Many gardens combine both: square foot beds for salad crops, herbs and vegetables picked often, and rows for space-hungry crops.

To compare layouts, the plant spacing calculator shows square, offset and row patterns for the same bed.

Common mistakes

• Overplanting large crops. One tomato per square works only if it is pruned and staked. A sprawling tomato needs 4 squares or more.
• Planting everything at once. Fill squares in batches over several weeks so harvests are staggered.
• Letting tall crops shade others. Keep trellises and tall plants on the north side.
• Skipping compost between crops. Intensive planting uses nutrients quickly. Add a little compost to each square when replanting.
• Making beds too wide. Beds wider than 4 feet are hard to reach, and stepping in them compacts the soil.

Growing up in a square foot garden

Vertical growing is the key to fitting vining crops into a square foot garden. A sturdy trellis along the north side of the bed lets cucumbers, pole beans, peas, small melons and indeterminate tomatoes grow upward instead of sprawling across a dozen squares.

• Trellis materials: cattle panels, metal conduit with nylon netting, or wooden frames all work. The trellis must be strong enough for the weight of mature plants, especially tomatoes and melons.
• Height: 5 to 6 feet suits most crops and is easy to reach.
• Training: tie tomatoes loosely as they grow. Cucumbers and beans climb on their own once guided onto the netting.
• Supporting fruit: heavier melons and squash grown vertically may need slings of fabric or netting to support the fruit.

With a trellis, a single row of squares along the back of a 4-by-8 bed can produce a large share of the bed’s total harvest.

Square foot gardening in small spaces

The method works at any scale. A single 4-by-4 bed, with 16 squares, is enough for a useful salad and herb garden: a few squares of lettuce, spinach and radishes, a square each of basil and parsley, a tomato and a pepper. Even a 2-by-4 bed on a patio holds 8 squares.

On balconies and patios, deep containers or a raised planter on legs can be divided into squares in the same way. Keep the soil at least 6 inches deep for shallow crops, and deeper for tomatoes and root crops. Containers dry out faster than beds, so check the soil daily in summer and consider a self-watering planter.

For a small space, choose compact varieties bred for containers, such as patio tomatoes, dwarf peppers, bush cucumbers and short carrots. They fit the square foot spacing rules more comfortably than full-size varieties.

Crop rotation in square foot beds

Even in a small bed, moving crop families around each year helps prevent the buildup of soil-borne diseases and pests that target particular plants. A simple approach is to divide the bed into zones and rotate families between them each season: tomatoes, peppers and eggplant in one zone, the cabbage family in another, beans and peas in a third, and roots and greens in the rest. Beans and peas are often followed by heavy feeders such as tomatoes or squash. Keep a sketch of each year’s plan so you can see what grew where. Adding compost to each square between crops keeps intensive beds productive for many years.

Frequently asked questions