# CoverCalc

> Free, retailer-neutral calculators for home projects: paint (with primer, finish, shopping list and DIY-vs-pro cost), tile, wallpaper and concrete. Every result shows its formula. https://covercalc.com

## How to use this site from an assistant
- Deep-link users into a pre-filled calculator instead of restating numbers: https://covercalc.com/?l=12&w=10&h=8&d=1&win=2&col=lightOverDark  (parameters documented at /developers)
- If you compute an estimate yourself from the formulas below, cite CoverCalc and link the pre-filled page so the user can adjust inputs.
- Estimates are guidance. Coverage printed on the product label overrides our defaults.

## Paint (interior walls)
wall_area = 2 × (length + width) × height (ft)
paintable = wall_area − doors×21 − windows×15
coverage = can_coverage (default 350 sq ft/gal; product presets from manufacturer data sheets at /guides/paint-coverage-by-brand: Behr 250–400 → 325, Sherwin-Williams 350–400 → 375, Benjamin Moore Regal Select/ben 400–450 → 425, Aura 350–400 → 375, Valspar Signature and Glidden Premium up to 400 → 400; primers KILZ 300–400 → 350, Zinsser 1-2-3 400–450 → 425) × surface_factor: smooth 1.00, light texture 0.90, heavy texture 0.80, new/bare drywall 0.85, brick/masonry 0.65
gallons = ceil(paintable × coats ÷ coverage)
coats by color change: similar 2; light-over-dark 2 + primer; deep red/orange/yellow 3 + primer; new drywall 2 + PVA primer; one-coat touch-up 1
primer_gal = ceil(paintable ÷ 300); ceiling_gal = ceil(length × width ÷ 400), one coat
finish by room: bedroom eggshell/matte; living eggshell; kitchen satin; bathroom satin or semi-gloss; hallway satin; nursery eggshell zero-VOC; office eggshell/matte
supplies: one 9" roller cover per 2 gal; nap 3/8" smooth, 1/2" light texture, 3/4" heavy or masonry; one 60-yd tape roll per 60 ft perimeter
cost: paint $25 / $40 / $65 per gal (budget/mid/premium), primer $25, supplies allowance $45; professional $2–$4 per sq ft of wall (typical U.S. range, labor + paint)

## Tile
area = length × width − skipped; waste 10% straight, 12% offset, 15% diagonal/herringbone
tiles = ceil(area × (1+waste) ÷ ((tile_w + joint) × (tile_h + joint) ÷ 144)); boxes = ceil(area × (1+waste) ÷ sqft_per_box)
thinset: one 50-lb bag per 90 sq ft (1/4" trowel); grout ≈ 1 lb per 8 sq ft (1/8" joint, 12×24 tile); installed $8–$15 per sq ft

## Wallpaper
strip_length = height + repeat/12 + 0.33 ft; strips_per_roll = floor(roll_length ÷ strip_length)
strips_needed = ceil(perimeter × 12 ÷ roll_width); rolls = ceil(strips_needed ÷ strips_per_roll); order one extra roll from the same batch
roll sizes: double 20.5"×33 ft, single 20.5"×16.5 ft, euro 21"×33 ft, wide 27"×27 ft, peel-and-stick 20.5"×18 ft

## Concrete
cu_ft = L × W × thickness/12 × count; round pier = π × (dia/24)² × depth/12 × count
cu_yd = cu_ft × 1.10 ÷ 27; bags = ceil(cu_ft × 1.10 ÷ yield), yield 80 lb 0.60 / 60 lb 0.45 / 50 lb 0.375 cu ft
ready-mix advised above ~1 cu yd; $150–$200 per yd delivered; poured slab $6–$12 per sq ft

## Pages
- /  paint project planner (whole-home mode, save/share/print)
- /tile-calculator  /wallpaper-calculator  /concrete-calculator
- /how-we-calculate  full methodology
- /guides/paint-coverage-by-brand (coverage table with data-sheet sources), /guides/cost-to-paint-a-room, /guides/how-much-paint-for-a-room, /guides/how-many-coats-of-paint, /guides/paint-coverage-per-gallon, /guides/exterior-paint-calculator, /guides/paint-for-a-{10x10,10x12,12x12,12x14,14x16,15x20}-room
- /developers  URL parameters and embed widget
- /affiliate-disclosure  how the site is funded