How much material do you need?

Calculators

Why use these calculators

Buying too little means a second trip to the store and, for things like tile and paint, the risk that the next batch won't match. Buying too much wastes money and leaves heavy leftovers in the garage. Each calculator on this site:

• Shows its formula and a worked example, so you can see exactly how the number was reached.
• Rounds to what stores sell, such as whole bags, boxes, rolls and sheets, rather than leaving you with "3.7 boxes".
• Includes a waste allowance where it matters, with guidance on what percentage to use.
• Gives metric equivalents such as liters, square meters and cubic meters where useful.
• Runs in your browser. Nothing you enter is sent anywhere, and the pages load quickly on a phone at the hardware store.

Project guides

• How to Measure the Square Footage of a Room
  Step-by-step guide to measuring square footage for flooring, tile and paint: rectangles, L-shaped rooms, triangles, circles, walls and converting inches to feet.
• Bagged Concrete vs Ready-Mix: Which Should You Use?
  When to mix bags of concrete yourself and when to order a ready-mix truck. Compare effort, cost factors, strength and the break-even point for slabs and footings.
• How Much Extra Material Should You Buy?
  A practical table of waste allowances for flooring, tile, drywall, paint, concrete, mulch and gravel, with the reasons each material needs extra and how to avoid overbuying.
• How Many Coats of Paint Do You Need?
  How many coats of paint and primer you need for new drywall, color changes, dark colors, ceilings and trim, with worked gallon estimates and a decision table.
• How Thick Should a Concrete Slab Be?
  Recommended concrete slab thickness for patios, walkways, sheds, hot tubs, driveways and garages, with concrete volume per 100 sq ft, base depth and control joint spacing.
• Tile Spacing and Grout Joints: A Practical Guide
  How wide grout lines should be for floor, wall, rectified and large-format tile, sanded vs unsanded grout, and how joint width changes tile and grout quantities.
• Flooring Waste for Diagonal and Herringbone Layouts
  Why diagonal, herringbone and chevron floors need more material, typical waste percentages by pattern, worked box counts and layout tricks that reduce cut waste.
• How Deep Should Mulch Be? Depth by Bed Type
  Recommended mulch depth for flower beds, shrub borders, trees, vegetable gardens, paths and playgrounds, with cubic yards per 100 sq ft, a worked yard estimate and top-up advice.
• Best Gravel for Driveways: Types, Sizes and Layers
  Compare driveway gravel types (#3, #57, #411, crusher run, pea gravel), how to layer a gravel driveway, depths for each layer and a worked tonnage estimate.
• How Many Drywall Sheets Do You Need, and What Will It Cost?
  Count drywall sheets with the area method and the wall-by-wall layout method, choose 4x8 vs 4x12 and thickness, and build a full material cost estimate for a room.
• Fence Post Spacing: How Far Apart Should Posts Be?
  Typical fence post spacing for wood, vinyl, chain link, split rail and wire fences, how deep to set posts, how to space posts evenly on any run, and concrete per post.

Popular quick answers

All results are estimates for planning. Product coverage and yields vary, so check the label and confirm large orders with your supplier.