About CalcTheJob

CalcTheJob is a set of free calculators for the materials that go into home improvement, DIY and landscaping projects — concrete, pavers, asphalt, gravel, drainage stone, sand, topsoil, mulch, fencing, decking, flooring, tile, drywall, paint and roofing. Each one answers the practical question you’ll face at the store or the supply yard: how many bags, tons, boxes, sheets, gallons or bundles do I need?

Who runs this site

CalcTheJob is an independent website operated under the name CalcTheJob. It is not owned by, or affiliated with, any manufacturer, retailer or contractor, and no product maker pays to be mentioned. We don’t present ourselves as engineers or licensed contractors: the calculators estimate material quantities from published product data and standard geometry, and each page shows its sources so you can check them yourself. Corrections are welcome at contact@calcthejob.com.

How we build each calculator

The short version is below; the full version, calculator by calculator, is on our Methodology & Sources page.

• Start from what you buy. Results are in the units products are actually sold in — 40, 60 and 80 lb bags, tons and cubic yards, boxes, sheets and bundles — not just raw volume.
• Standard geometry. Areas and volumes use plain formulas: length × width × depth for slabs and beds, πr² for round shapes, and a slope factor of √(1 + (rise ÷ 12)²) to turn a roof’s footprint into its sloped area. Cubic feet are converted with 27 cu ft = 1 cubic yard and 2,000 lb = 1 short ton.
• Published product figures. Bag yields, coverage rates and packaging come from manufacturer data sheets — for example, the 0.60 cu ft yield of an 80 lb bag of concrete mix, the square-foot coverage of a 50 lb bag of thin-set by trowel size, or 370 ft of drywall tape per 1,000 sq ft of board. Where products differ, we use a typical value and let you type in the number from your own label.
• Codes and public guidance. Where a building code or public agency sets or publishes a figure — deck joist spacing in the International Residential Code, aggregate weights used by state transportation departments, mulch depths recommended by university extension services — we use and cite it.
• Show the math. Every page explains the formula and works through real examples, so you can check the answer by hand.
• Test it. The calculation code is covered by automated tests that check results against worked examples and reference values.

Rounding and waste factors

• We round up, never down. You can’t buy 44.3 bags, so every count — bags, boxes, sheets, bundles, rolls, truck loads — is rounded up to the next whole unit. Volumes and weights are shown to at most two decimals.
• Waste is a separate, visible setting. Most calculators add 10% by default for cuts, breakage, spillage and uneven bases. Tile uses a pattern-based allowance (10% straight, 12% offset, 15% diagonal, 20% herringbone). You can change the percentage in each tool.
• When in doubt, err toward enough. Where a manufacturer publishes a range, such as thin-set coverage, we use the low end of coverage so you are less likely to run short. Leftover sealed bags or boxes can often be returned; a second trip mid-pour usually can’t be undone.
• Loose vs. compacted. Gravel and stone weights are loose, as-delivered figures. If you are building a compacted base, add the compaction allowance in the tool.

Sources and review

Each calculator page ends with a Sources & assumptions section listing the documents behind its numbers — for example QUIKRETE’s concrete mix data sheet, USG’s gypsum panel guides, the International Residential Code, the American Wood Council’s deck guide, state DOT estimating factors and university extension fact sheets — with links and the date we last checked them. All of them are collected on our Methodology & Sources page. When a manufacturer changes a product or a source moves, we update the page and its date.

What our calculators don’t do

They estimate quantities. They don’t design structures, check spans or loads, or replace your local building code. For footings, deck framing, roof structure and anything that carries weight, talk to your building department or a licensed professional. See our Terms of Use.

Privacy

All calculations run in your browser. Nothing you type into a calculator is sent to our servers. Details are in our Privacy Policy.

Advertising

The site is free and supported by advertising. Ads are kept separate from the calculators and their results, and advertisers have no influence over our formulas or content. We don’t recommend specific brands; when we name a manufacturer, it is only to cite the data we used. Read how ads and cookies work in our Privacy Policy.

Get in touch

Found an error or want a calculator we don’t have yet? Email contact@calcthejob.com — see the contact page for what to include.