DIY & Materials
DIY & Materials Calculators
Calculator Matters’ DIY & Materials category answers the question every home project starts with — how much do I actually need to buy — starting with concrete for slabs, footings, and columns, and paint for a room repaint. This is deliberately separate from Home & Energy, which sizes engineered systems like solar capacity or insulation R-value; DIY & Materials is about raw material quantity for hands-on projects. Further tools are planned, each held to the same sourced, checkable-formula standard before it publishes.
Concrete & Masonry
Painting
Who this is for
Built for homeowners and DIYers pricing a project before buying materials — the Concrete Calculator for a pour, and the Paint Calculator for a repaint.
How to choose a calculator
Use the Concrete Calculator for a rectangular slab or footing, or a circular slab or column — enter the dimensions and a waste factor to get cubic yards (how ready-mix is ordered) and 40, 60, and 80 lb bag counts (how small DIY pours are bought) side by side.
Use the Paint Calculator for a room repaint — enter its dimensions, doors, windows, and coats to get gallons needed, with an adjustable coverage rate for textured or porous surfaces.
Compare diy & materials calculators
What each calculator is best for, the main inputs it needs, what it shows, and what to keep in mind.
| Calculator | Best for | Key inputs | Shows | Keep in mind |
|---|---|---|---|---|
| Concrete Calculator | Ordering the right amount of concrete before a pour, in yards or bags | Shape (rectangular or circular), length, width or diameter, thickness or depth, waste factor | Cubic yards needed, and 40, 60, and 80 lb bag counts | Volume only — does not size a footing for load, specify mix strength, or include reinforcement |
| Paint Calculator | Buying the right number of gallons before a repaint, walls and ceiling included | Room length, width, ceiling height, doors, windows, coats, coverage rate | Gallons needed and gallons to buy, rounded to the nearest half gallon | Does not include primer, trim, or spray-application coverage differences |
Best calculator path
- Choose a rectangular or circular shape and enter the dimensions for the Concrete Calculator, or the room dimensions, doors, windows, and coats for the Paint Calculator.
- Adjust the waste factor (concrete) or coverage rate (paint) for your specific job, then read off the order-ready quantity.
- Check each calculator's formula section to see exactly how the quantity was reached, not just the final number.
- Read the limitations before ordering — concrete for anything structural or permitted, paint for primer and trim, which aren't included.
Common mistakes and limits
- Concrete: skipping the waste factor — forms are never perfectly level and some mix is always lost to spillage and overfilling, so ordering the bare calculated volume tends to come up short.
- Concrete: treating a circular field as the radius instead of the diameter — the calculator asks for diameter, matching how tube and post sizes are usually specified.
- Paint: forgetting a second coat, or forgetting that primer is a separate estimate at a lower coverage rate than finish paint.
- Paint: trying to pour an L-shaped room or slab into one rectangle — break complex shapes into simple rectangles and add the results.
When not to rely on calculators alone
These calculators estimate material quantity only. The Concrete Calculator doesn’t size a footing for a given load, specify a concrete strength mix, or account for reinforcement — confirm anything structural or permitted with a structural engineer or the local building department. The Paint Calculator doesn’t include primer, trim, or account for spray application — check the coverage rate printed on the specific can you buy.
Source and calculation basis
The Concrete Calculator’s volume formulas are standard geometry, with bag yields cross-verified from two independent manufacturer technical data sheets (Quikrete and Sakrete) and a waste factor following NRMCA’s published CIP 31 guidance. The Paint Calculator’s coverage rate and door/window deductions are cross-verified from Sherwin-Williams, Benjamin Moore, Behr, and Lowe’s. See each calculator’s own Sources section for the full citations.
See the Methodology for how calculators are built and reviewed, who runs the site, the Disclaimer for the full terms, and the Contact page to report an issue.
Frequently asked questions
Common questions about diy & materials calculators and how to use them.
What calculators are in the DIY & Materials section?
The Concrete Calculator turns a slab, footing, or column's dimensions into cubic yards and a count of 40, 60, or 80 lb pre-mix bags, using yields cross-verified from two independent manufacturer technical data sheets. The Paint Calculator turns a room's dimensions, doors, windows, and coats into gallons needed, using a coverage rate cross-verified from Sherwin-Williams, Benjamin Moore, Behr, and Lowe's. More material calculators covering flooring and outdoor projects are planned, each held to the same sourced, checkable-formula standard before publishing.
How is this different from Home & Energy?
Home & Energy sizes engineered systems against standards — solar panel capacity, insulation R-value, roofing and fencing structure. DIY & Materials answers a narrower, more practical question: how much raw material do I need to buy for a hands-on project, starting with concrete and paint.
Does this section store or share the figures I enter?
No. Every calculation in this section runs entirely in your browser using your device’s own JavaScript engine — nothing you type into any calculator here is sent to or stored on our servers.
Explore other categories
Browse the other calculator categories on Calculator Matters.