Rows Per Bed: Set Spacing or Set Row Count

Rows per bed is the question here. Set the spacing to find how many rows fit, or set the number of rows to find the spacing that fits.

The two modes on the same bed

The Row Spacing Calculator has two modes. In spacing mode you enter a row spacing and the calculator works out how many rows fit. In count mode you enter a number of rows and the calculator works out the spacing that fits. Both modes also give total row length, which is rows times bed length.

The standard bed is 1.2 m wide and 3 m long, with a 15 cm margin at each edge. The imperial version is 4 ft wide and 10 ft long, with a 6 in margin. Keep the two versions separate, as the defaults are rounded equivalents, not exact conversions.

Usable width equals bed width minus 2 times margin. On the metric bed it is 90 cm. On the imperial bed it is 36 in.

Spacing mode in metric

Set 30 cm spacing on the metric bed, with the 15 cm margin at each edge. Rows equals floor of 90 divided by 30 plus 1, which is 4 rows. Total row length is 12 m.

The plus 1 matters because the first row sits one margin in from the first edge and the last row sits one margin in from the far edge, so three gaps join four rows. At 45 cm spacing the answer is 3 rows and 9 m. At 60 cm it is 2 rows and 6 m. At 90 cm it is also 2 rows and 6 m.

Count mode in metric

Set 4 rows on the same metric bed, with the same 15 cm margin. Spacing equals 90 divided by 3, which is 30 cm, the same answer as spacing mode gave from the other direction.

The table below shows the spacing each set row count needs on the metric bed.

Rows wanted	Spacing needed
2	90 cm
3	45 cm
4	30 cm
5	22.5 cm
6	18 cm
8	12.9 cm

Two rows need 90 cm, three rows need 45 cm, five rows need 22.5 cm, six rows need 18 cm, and eight rows need 12.9 cm, which is 12.857 cm shown to one decimal place. Total row length is 6, 9, 12, 15, 18, and 24 m for 2, 3, 4, 5, 6, and 8 rows.

The same bed in imperial

Set 12 in spacing on the 4 ft bed, 10 ft long, with a 6 in margin. Rows equals floor of 36 divided by 12 plus 1, which is 4 rows. Total row length is 40 ft.

In count mode, set 4 rows on the same bed. Spacing equals 36 divided by 3, which is 12 in.

The table below shows the spacing each set row count needs on the imperial bed. Keep it separate from the metric table above.

Rows wanted	Spacing needed
2	36 in
3	18 in
4	12 in
5	9 in
6	7.2 in
8	5.1 in

Two rows need 36 in, three rows need 18 in, five rows need 9 in, six rows need 7.2 in, and eight rows need 5.1 in, which is 5.143 in shown to one decimal place. Total row length is 20, 30, 40, 50, 60, and 80 ft for 2, 3, 4, 5, 6, and 8 rows.

When to use each mode

Use spacing mode when the crop spacing is fixed and you want to know how many rows fit. The page FAQ band is 30 cm for small crops such as carrots and lettuce, and 45 to 90 cm for larger crops, or 12 in and 18 to 36 in in imperial.

Use count mode when the bed must hold a set number of rows. For example, 3 rows in the standard bed need 45 cm in metric and 18 in in imperial. Check that spacing against the crop band before you sow, and change the row count or the bed if it is outside the band.

Choose the mode that matches the fact you already know: spacing mode if you know the spacing, count mode if you know the row count.

The reverse formula and the minus 1

Spacing equals usable width divided by rows minus 1. The minus 1 exists because spacing is the gap between rows, and the number of gaps is always one less than the number of rows.

Work the metric 4 row case. Usable width is 90 cm, rows minus 1 is 3, and spacing equals 90 divided by 3, which is 30 cm. Divide by 4 instead, and you get 22.5 cm, the spacing for 5 rows, not for 4 rows.

The forward formula has a plus 1 for the same reason.

The one row case

Spacing for 1 row cannot be worked out, because rows minus 1 is zero and dividing by zero has no answer.

One row is the single centre row case for wide crops, with no second row to measure a gap to.

Four margin mistakes to avoid

First, a margin of 0 gives more rows, but the page warns against it. On the 1.2 m bed at 30 cm spacing with a 0 margin, usable width is 120 cm, and rows equals floor of 120 divided by 30 plus 1, which is 5 rows, yet plants right at the edge dry out and spill onto paths.

Second, the half spacing margin and the fixed 15 cm margin give different answers at the same spacing, so always state which margin rule you used. At 45 cm spacing, the fixed 15 cm margin gives 3 rows, while the half spacing margin of 22.5 cm gives 2 rows. At 90 cm spacing, the fixed margin gives 2 rows, while the half spacing margin of 45 cm gives 1 row. The half spacing rule is the page recommended rule, and the fixed 15 cm margin is the page default margin.

Third, a margin at or above half the bed width leaves no usable width, so keep the margin below half the bed width. On a 1.2 m bed, half the bed width is 60 cm, so a margin of 60 cm leaves usable width 0.

Fourth, forgetting the plus 1 gives the wrong row count. Dividing the usable width 90 cm by 30 cm gives 3, which counts the gaps and misses the last row. The correct count is 4.

Page guidance to follow

Mark rows with string before sowing, after entering bed width and length, choosing a mode, and setting a margin from each edge.

Rows often run north to south for even sun.

Raised beds do not necessarily need rows. Many gardeners plant in a grid or offset pattern instead.

Direct sown rows can be closer than transplant rows, as direct sown crops are sown where they will grow.

Paths between beds are not included. Total row length counts only the rows inside the bed.

What this calculator does not give

This calculator gives rows, spacing, and total row length only, from bed width, bed length, row spacing or row count, and an edge margin. It gives no plants per row, no plants per bed, no density, no seeds, no yield, and no cost.

The page figures are starting points to edit, not universal constants, and the page was last reviewed in November 2026.

Related calculators on the same site

The Crop Spacing Calculator, the Plant Spacing Calculator, the Garden Bed and Path Layout Calculator, and the Garden Area Calculator cover different questions on the same site.

Frequently asked questions

Q: How many rows per bed fit a 1.2 m bed at 30 cm spacing?
A: 4 rows, with a 15 cm margin at each edge, and 12 m of total row length on a 3 m bed.

Q: How do I work out the spacing for a set number of rows?
A: Spacing equals usable width divided by rows minus 1, where usable width equals bed width minus 2 times margin.

Q: When should I use spacing mode and when should I use count mode?
A: Use spacing mode when the crop spacing is fixed and you want to know how many rows fit. Use count mode when the bed must hold a set number of rows and you want to know the spacing that fits.

Q: What spacing does 1 row need?
A: No spacing can be worked out for 1 row, because rows minus 1 is zero. One row is the single centre row case for wide crops.

Q: Why does the margin change the row count?
A: The margin sets the usable width, and usable width sets the row count. At 45 cm spacing the fixed 15 cm margin gives 3 rows and the half spacing margin gives 2 rows, so always state the margin used.

Q: What does the Row Spacing Calculator not give?
A: It gives rows, spacing, and total row length only. It gives no plants per row, no plants per bed, no density, no seeds, no yield, and no cost.