Vegetable Garden Spacing Calculator and Harvest Scenario Tool

Preparing measurements and spacings

You can access the calculator after recording four values: the cultivable length and width in metres, then the distance between two plants in a row and between two rows in centimetres. Spacings are measured from centre to centre. Rows follow the length entered.

Measure a rectangle available for crops, excluding paths and obstacles. For an irregular area, first draw the truly usable sections on your vegetable garden plan. The RHS recommends a scale drawing to avoid overcrowding crops.

Choose distances based on the specific instructions for your variety and its cultivation method. The SNHF emphasises the importance of seed packet instructions, appropriate density, and thinning after seedling emergence. The number of positions for plants you intend to keep does not directly indicate the number of seeds to sow.

Also check the space required for mature growth and how long the crop will occupy the bed. To organise neighbouring crops, the University of Maryland distinguishes between growth above and below ground, time to maturity, and requirements for light, water, and nutrients. The calculator does not verify any of these criteria.

Understanding the calculated grid

Each position corresponds to the centre of a rectangular cell: one spacing along the row by one spacing between rows. The calculation retains only whole cells. At the ends of rows, centres remain at least half a spacing from the edge; at the sides, they remain at least half the between-row spacing from the edge. You can centre the set of cells within the bed by distributing the remaining space between the two edges.

This geometric convention defines the tool’s result. It does not set ideal margins for a crop or seek the maximum number of points that could otherwise be placed in the rectangle.

After converting all spacings to metres, the method is:

L = cultivable length; W = cultivable width
p = spacing along the row; r = spacing between rows
positions per row = floor(L / p)
number of rows = floor(W / r)
number of positions = floor(L / p) × floor(W / r)

The floor function means “take the lower integer”: 6.25 cells yield 6 positions. The form accepts either a comma or a full stop, up to three decimal places in metres and one decimal place in centimetres, allowing input precision to the millimetre. Dimensions and spacings must be strictly positive.

Reading the result without confusing area and positions

Here is an example calculation, with no assigned crop or recommended spacing. With a bed of 2.5 m by 1.1 m and spacings of 40 cm along the row and 30 cm between rows:

• along the length: 2.5 ÷ 0.4 = 6.25, thus 6 positions per row;
• along the width: 1.1 ÷ 0.3 = 3.66…, thus 3 rows;
• in total: 6 × 3 = 18 positions.

Dividing only the area by that of one cell would give approximately 22.92. Even rounded to 22, this result does not describe the whole cells that fit in this grid.

Orientation also matters. For another purely geometric example, 4 m by 1.2 m with 40 cm along the row and 60 cm between rows gives 10 × 2 = 20 positions. By swapping length and width, the same distances give 3 × 6 = 18 positions. Compare both layouts on the ground before choosing the one that suits your access and crops.

If one side is smaller than the corresponding cell, the result may be zero. This means no whole cell fits according to this convention; it does not prove that no plant could grow in the area.

Adding a yield assumption, if useful to you

The field for kilograms per plant is optional and initially empty. Leaving it empty counts only positions. Explicitly entering zero produces a zero-yield scenario.

If you provide a value, the calculation applies only this multiplication:

yield scenario in kg = number of positions × your assumption in kg per plant

This total assumes each position contains a plant that produces exactly the yield you entered. This is not an expected harvest. The calculation does not predict seedling emergence, survival or yield per plant; it provides no average per vegetable.

If you base this on your own past harvests, also keep a note of the variety, cultivation method and period to which they correspond. The multiplication helps compare assumptions; it does not verify that they will recur in your garden.