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Measure once.
Calculate once.
Buy it right.
Get it done.

Twenty calculators for every part of the project — indoor, outdoor, and advanced electrical tools for circuit load, wire size, and generator sizing. Switch to metric in the corner if you measure in meters and liters.

Indoor

Indoor Projects

Room Square Footage Calculator

Add up as many rooms as you need for a total square footage before pricing out paint, flooring, or trim.

Job: Room Size
Room 1
Room 2
How it works: each room's area = length × width; add every room together for the total, then divide by 9 for square yards. Example: a 12×10 ft room (120 sq ft) plus a 10×8 ft room (80 sq ft) adds up to 200 sq ft — about 22.2 square yards.
Browse the project guides to put this number to use →

Paint Calculator

Figure out how many gallons a room actually needs, including doors, windows, and a second coat.

Job: Interior Paint
How it works: wall area = (2 × length + 2 × width) × height, minus door and window area, × number of coats, ÷ coverage. Example: a 12×10 ft room with 8 ft walls, one door, two windows, and two coats needs roughly 2 gallons at 350 sq ft/gallon coverage.
Read the full guide: How Much Paint Does a Bedroom Actually Need? →

Flooring Calculator

Convert room size into square footage and boxes needed, with waste built in for cuts.

Job: Flooring
How it works: area = length × width, plus your waste percentage, divided by how many square feet each box covers, rounded up to a full box. Example: a 14×11 ft room (154 sq ft) with 10% waste needs about 170 sq ft of material — 9 boxes if each box covers 20 sq ft.
Read the full guide: How Many Boxes of Flooring Do You Actually Need? →

Tile Calculator

Figure out how many tiles a floor or wall needs, based on your exact tile size.

Job: Tile
How it works: area = length × width, plus waste, divided by the square footage of one tile. Example: a 10×8 ft floor with 12×12 in tiles and 10% waste needs about 88 tiles.
Read the full guide: Tile Layout Mistakes That Cost You Extra Boxes →

Drywall Calculator

Convert wall dimensions into the number of sheets you need to buy.

Job: Drywall
How it works: wall area minus door/window area, divided by sheet size. Example: a 12×10 ft room with 8 ft walls needs about 8 sheets of standard 4x8 drywall.
Read the full guide: Drywall Sheet Sizes — 4x8 vs 4x12 →

Wallpaper Calculator

Estimate rolls needed, with room left over for pattern matching and trimming.

Job: Wallpaper
How it works: net wall area divided by usable square footage per roll after trimming. Example: a 12×10 ft room needs about 7 rolls at 25 usable sq ft per roll.
Read the full guide: Wallpaper Pattern Repeat — The Number That Wrecks Your Roll Count →

Baseboard & Trim Calculator

Turn room perimeter into the number of boards to buy.

Job: Trim
How it works: perimeter minus doorway widths, plus waste, divided by board length. Example: a 12×10 ft room with one 3 ft doorway needs about 6 boards at 8 ft each.
Read the full guide: Baseboard Corners — Cope vs Miter →
Outdoor

Outdoor Projects

Mulch & Soil Calculator

Find the volume or bags you need for a bed or garden area, at any depth.

Job: Mulch & Soil
How it works: volume = length × width × depth, then converted to bags or bulk units. Example: a 20×6 ft bed at 3 inches deep needs about 1.1 cubic yards — roughly 15 bags at 2 cubic ft each.
Read the full guide: Gravel vs. Mulch — Which Is Right for Your Yard? →

Concrete Calculator

Find the volume and bags needed for a slab, footing, or pad.

Job: Concrete
How it works: volume = length × width × thickness, then ÷ bag size for bag count. Example: a 10×10 ft slab at 4 inches needs about 1.23 cubic yards — roughly 56 bags at 80lb each.
Read the full guide: Concrete Slab Basics — Thickness, Curing Time & Weather Windows →

Gravel Calculator

Estimate volume and total weight for a driveway, path, or drainage bed.

Job: Gravel
How it works: volume × density gives total weight. Example: a 20×10 ft path at 4 inches deep needs about 3.5 tons of gravel.
Read the full guide: Gravel Sizes Explained →

Fence Calculator

Turn fence line length into posts and panels needed.

Job: Fence
How it works: posts = (fence length ÷ spacing) + 1, panels = fence length ÷ panel width. Example: 120 linear ft with 8 ft spacing needs 16 posts and 15 panels.
Read the full guide: Fence Post Depth and Spacing →

Deck Calculator

Estimate decking boards needed, accounting for board width and gap spacing.

Job: Deck
How it works: deck area ÷ (board width + gap) gives total board length, plus waste, divided by board length. Example: a 16×12 ft deck needs about 35 boards at 12 ft each.
Read the full guide: Deck Board Spacing — Why That Small Gap Matters →

Sod Calculator

Convert lawn area into pallets of sod needed.

Job: Sod
How it works: lawn area plus waste, divided by square footage per pallet. Example: a 40×30 ft lawn needs about 3 pallets.
Read the full guide: Sod vs. Seed — When Each One Makes Sense →

Roofing Calculator

Turn a footprint measurement (like one from Google Maps) into shingle bundles needed, accounting for roof pitch.

Job: Roofing
1 2 3 4

How to get your footprint number

  1. Open Google Maps, right-click your address, choose "Measure distance."
  2. Click each corner of your roof in order — skip the peak, like the diagram above.
  3. Copy the area total into the field below.
How it works: actual roof area = footprint × pitch multiplier (accounts for slope), plus waste, divided by bundle coverage. A 6/12 pitch multiplies footprint by about 1.118. Example: a 1,500 sq ft footprint at a 6/12 pitch works out to about 1,677 sq ft of actual roof — roughly 60 bundles at 33.3 sq ft each.
Read the full guide: Measuring Your Roof From Google Maps →

Siding Calculator

Turn your house's perimeter into panels or squares of siding needed.

Job: Siding
How it works: perimeter × wall height, minus door and window area, plus waste, divided by panel coverage. Example: a 160 linear ft home with 9 ft walls, two doors, and eight windows needs about 92 panels at 16 sq ft each.
Read the full guide: How Many Siding Panels Does Your House Need? →
Advanced

Advanced Tools

⚡ Electrical Calculators

Electricity cost, watts and amps, circuit load, wire size and voltage drop, and generator sizing, for planning projects and checking circuits.

Job: Electrical
Estimates only. Electrical code varies by location, so check your local code and use a licensed electrician for wiring work.
Open the electrical calculators →