Concrete Volume and Bag Calculator

Who this is for

Turn each pour into volume, bags and cost. List every slab, footing, step and post hole with its size, then the yield and price from the bag you are buying.

Homeowners laying a shed base, a path or a step, setting fence or gate posts or pouring a small footing, and anyone checking the quantity on a merchant's or builder's quote.

What this helps you track

• The volume of every slab, footing, step and post hole you plan to pour
• Round holes worked out from their diameter and depth
• Bags of each mix to buy, from the yield on the bag and your own wastage figure
• The cost of each product and of the whole job

How to use it

1. Write the job, who measured it and the date at the top.
2. Give each pour a row: length and width in metres, or the diameter in metres for a round hole, then the depth in millimetres and how many of that pour there are.
3. The volume of each row and the total are worked out in the browser and the workbook; on paper, multiply length by width by depth in metres, then by the count.
4. In the bags table, give each product a row with the volume it has to fill, the yield per bag in cubic metres from the bag, your wastage percentage and the bag price.
5. Bags are rounded up to whole bags and costed; buy those, and keep the receipt in case any go back unopened.

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

Where does the yield per bag come from?

From the bag or the product page, which states roughly how much finished concrete one bag makes. The sheet supplies no yields, because they differ between products and bag sizes, so enter the figure for the mix you are buying.

How are post holes worked out?

A round hole is treated as a cylinder: 3.1416 times the diameter squared, divided by four, times the depth. The post itself is not taken off, so the figure for each hole errs on the generous side.

What wastage percentage should I use?

The sheet does not suggest one. Spillage, uneven ground and a dig that comes out deeper than planned all use extra, so use your own judgement or your supplier's advice and enter it on each product row.

Can I use it for ready-mixed concrete?

Yes. Enter a yield of 1 and the price per cubic metre, and the bags column shows whole cubic metres. If your supplier sells part loads, order from the volume itself and ask how they round it.

Can I put two products on one sheet?

Yes. A general mix for a slab and a post-fix product for the holes each get their own row in the bags table, with the volume that product has to fill copied from the pours above.