Decking Materials Calculator

Who this is for

Count the boards, joists and fixings for a deck. Enter your board size, gap, joist spacing and fixings per crossing, measure each section, then cost the order.

Homeowners building a timber or composite deck themselves, and anyone checking a landscaper's materials list or a merchant's quote before buying.

What this helps you track

• Rows of boards across each section from the board width and gap
• Boards per row and boards in total at your board length
• Joists at the spacing you have chosen, and the metres of joist timber
• Fixings from the number used where each board crosses a joist
• Posts, beams, fascia and step boards costed alongside

How to use it

1. Write the deck and its location, then the board width and gap in millimetres and the board length in metres from the product.
2. Enter your joist spacing in millimetres and the fixings per crossing from the board maker's or fixing packet's instructions; the sheet supplies neither.
3. Split the deck into rectangles and measure each: length is the way the boards run, width is across them.
4. Rows, boards, joists and fixings are worked out in the browser and the workbook; on paper, divide and round each figure up.
5. Copy the totals into the order table, add posts, beams, fascia and step boards from your design, and enter pack sizes and prices to cost it.

Formats

• Printable PDF (A4 and US Letter)
• Fillable PDF with form fields
• Fill in online, saved in your browser
• Excel / Google Sheets workbook

The printable is laid out inside a box that fits both A4 and US Letter, so the two files are identical and neither one is scaled. The fillable PDF has real form fields. The workbook uses plain formulas only — SUM, IF, COUNTIF and the like — so it opens in Excel, LibreOffice and Google Sheets without anything breaking, and every calculated cell is grey so you can see which figures it worked out.

How to print

Download the A4 or US Letter file to match the paper in your printer, open it in a PDF reader and print at 100% — not "fit to page", which shrinks the writing space. Both files leave a 14 mm margin, which clears the unprintable edge on home printers. To print the online version with your entries in it, use the Print this sheet button, which prints only the sheet and none of the page around it. More on printing.

Questions

Which way is length and which is width?

Length is the direction the boards run. Width is across the boards, so it sets how many rows of boards you need. Joists run across the boards, spaced along the length at your chosen spacing.

Where does the joist spacing come from?

From your design and the board maker's instructions, which often set a maximum span for their boards. The sheet supplies no spacing; enter the figure that applies to your boards and your use of the deck.

Why are boards per row rounded up?

You cannot buy part of a board, so each row is counted in whole boards. Offcuts are not reused in the sum, which makes the total generous; you can lower it in the order table if your layout lets offcuts start the next row.

Does it work out posts and beams?

No. Their number and size depend on the height, the ground and your design, so add them to the order table from your plans or your builder's drawings.