Interior & Remodeling
Inside the house, estimating splits into two kinds of problems: coverage math (how many gallons, sheets, boxes for these walls and floors) and budget math (what a kitchen, bath, or basement costs by line item). These six calculators handle both.
Walls and floors: divide by coverage, round up to the store
Every surface takeoff is the same five moves: measure the real surface, subtract what isn't painted or covered (doors, windows), divide by the product's coverage rate, add a waste factor, and round up to what the store actually sells. The paint calculator runs it for walls — openings out, coats and texture in, gallons and primer out. The drywall calculator does sheets by panel size, then keeps going into the consumables people forget: joint compound, tape, and screws, which is where drywall budgets quietly leak.
Flooring adds one twist: the waste factor depends on the install pattern, not just the material. A straight-lay plank floor wastes ~5–7%; a diagonal or herringbone layout can push 15%. The flooring calculator applies layout-specific waste and converts to boxes — because you buy boxes, not square feet — with the reasoning documented in the waste factors guide.
Remodels: itemized lines beat headline numbers
"A kitchen costs $25,000" is a coin flip, not an estimate. Real budgets are lists, and each room has one line that dominates. In the kitchen remodel cost calculator, cabinets and countertops both scale off the cabinet run's linear footage and together eat roughly 40–50% of a mid-range budget — cabinet grade is the single biggest lever you control. In the bathroom remodel cost calculator, the wet area rules: waterproofing and tile take the largest trade share (28%), and upgrades like a tub-to-shower conversion get their own lines because each one is a four-figure decision.
Basements flip the logic again: most of the work scales per square foot, but the items that don't — a bathroom, code-required egress windows for any bedroom, moisture remediation — are exactly the ones that blow budgets. The basement finishing cost calculator prices them as separate lines and flags a bedroom layout entered with zero egress windows, because a bedroom without one isn't legally a bedroom in most U.S. jurisdictions.
All three remodel tools end the same way: an honest range (±15%) around a region-adjusted total, with every rate editable and stamped July 2026. Swap in a contractor's real quote on any line and watch what it does to the whole — that's how you find the negotiable 20%.
Sequence the rooms like the trades do
If you're doing several of these projects in one season, run the messy, structural work first and the coverage work last: moisture and framing (basement), then rough plumbing and electrical (kitchen/bath), then drywall, then paint, then flooring — paint before floors so drips land on subfloor, floors before baseboard so the trim hides the expansion gap. Each calculator stands alone, but entered in that order the numbers become a project plan, not just a price check. The full method is written up in how to estimate materials.