About
On DIY Totals you get a free set of material calculators covering concrete, stairs, roofing and everyday conversions for home projects. The results show how much material to buy, with extra for spills and off-cuts, so you know what to expect before you shop.
Every figure on DIY Totals starts from US retail averages for material densities and from reference retail prices. The month when each was last checked appears next to it. Our calculators assume published product yields: for example, an 80 lb bag of concrete yields 0.6 cubic feet, and a 60 lb bag yields 0.45, per the QUIKRETE specification linked on the concrete pages. Every calculator adds a waste factor, extra material for spills, uneven ground and offcuts, and you can adjust it on the page. Concrete, shingles and deck boards default to 10%, while pavers default to 5% for running or stack bond, 10% for herringbone and 15% for diagonal. The calculator rounds up first, then you buy whole bags, bundles or boards. Stair pages link to the International Residential Code, and the stair calculator applies that code's residential riser limit. A page linked under this text, labeled "Formulas and worked examples", brings every formula, its default assumptions and a worked example together on one page. These results are for planning, not for a formal quote; the number that counts when you buy is the price from your supplier. If you see a figure that looks wrong, report it through the contact page, naming the page, the figure you expected, and the figure you saw.
What level of accuracy should I expect, and can these numbers take the place of a supplier quote?
The numbers are planning estimates built from US retail averages for material densities, reference retail prices, and standard product yields. Use them to budget and decide how much material to order, but they are not a substitute for a supplier's quote. A supplier can factor in local delivery costs, discounts and product variations that a calculator cannot.
What does the as-of month on a figure mean for someone buying today?
Prices and densities change over time, so each figure carries the month it was last checked. If you are buying today, use the figure as a starting point, and check current prices at your local supplier.
Where do the bag counts come from?
Bag counts come from the manufacturer's published yields, such as the QUIKRETE specification for concrete, and we add a 10% waste factor before rounding up to whole bags. That is why the answer you see is a shopping list, not a precise volume.
What should I do when a figure looks wrong?
Tell us through the contact page. Include the page you were on, the figure you expected, and the figure you saw. That gives us enough to check the calculation and the assumptions behind it.