THE GUIDE / choosing
Compare polytunnel bed layouts before you choose
Compare two bed-and-path footprints in the size calculator, then check a drawing against your plot and supplier information.
Compare the bed-and-path layouts you might use, then take the more promising drawing to a supplier. Use the polytunnel size calculator to compare them. Footprint area and bed area answer different questions: one includes the paths in the calculator's layout, while the other counts only the beds. Neither number tells you which layout will grow more or whether a particular frame will fit.
Compare two versions in the calculator
Calculate your first layout, then choose Keep this layout. That saves one snapshot on the current page. Change the inputs and calculate another version to see the table labelled Current minus saved. Width, length, total footprint and bed area appear for both versions, with the signed difference between them.
A negative difference means the current measurement is smaller than the saved one; a positive difference means it is larger. Editing the inputs does not change the saved snapshot. Choosing Keep this layout again replaces it, and Clear saved layout removes it. Reloading the page also clears it. The calculator does not save this comparison between visits.
Change inputs in a way you can interpret
To see what one choice changes, keep the others fixed. For example, compare one bed with two while retaining the same bed dimensions, path width and door position. Then try a different path width as a separate comparison. You can combine changes later to represent a layout you are considering.
The calculator assumes identical rectangular beds placed side by side. It includes one path between neighbouring beds, and a single bed has one path alongside it. An end door adds no cross-aisle strip; a side door adds one path-width strip across the end, increasing the calculated layout length. These are the calculator's drawing conventions. They do not decide where a real path or door should go.
Worked comparison
These examples use chosen inputs to show how the measurements differ. They are not recommended bed or path dimensions.
Layout A, saved: two beds, each 4 m long and 1 m wide, a 0.6 m path between them, and an end door. The footprint width is 2 × 1 + 0.6 = 2.6 m and the length is 4 m, giving 2.6 × 4 = 10.4 m² total footprint. Bed area is 2 × 4 × 1 = 8 m².
Layout B, current: one bed, 3 m long and 1.2 m wide, a 0.5 m side path, and a side door. With one bed, the path runs alongside it, so the width is 1.2 + 0.5 = 1.7 m. The side door adds a 0.5 m cross aisle, making the length 3 + 0.5 = 3.5 m. Its total footprint is 1.7 × 3.5 = 5.95 m²; bed area is 1 × 3 × 1.2 = 3.6 m².
With B current and A saved, the results are:
| Measurement | Saved A | Current B | Current minus saved |
|---|---|---|---|
| Footprint width | 2.60 m | 1.70 m | −0.90 m |
| Footprint length | 4.00 m | 3.50 m | −0.50 m |
| Total footprint | 10.40 m² | 5.95 m² | −4.45 m² |
| Bed area | 8.00 m² | 3.60 m² | −4.40 m² |
Here B uses a smaller footprint and has less bed area than A. The arithmetic describes only these entered rectangles; it does not rate the layouts for growing, access or suitability.
Take the drawing to the next check
Mark out the layout you want to examine and walk the routes you have drawn. If you need to change the arrangement, update the inputs and calculate it again. The tool does not choose an access route or a suitable path width for your plot.
Use the labelled dimensions on the drawing, not a ruler on the screen or printout. Ask the supplier for a dimensioned plan for the exact model and size, including the usable width, door opening and any installation clearances they specify. Compare that information with your drawing; the calculator's footprint is not evidence of product fit.
For a single-layout starting point, see what size polytunnel?. How we compare explains how product specifications are recorded. This page compares layout arithmetic only; it does not rank products or recommend crops.