Window Sizing & Quantity
The deterministic sizing & quantity cluster — the highest-demand window queries: a united-inches calculator (the signature sizing metric, UI = width + height), a window area / square-footage calculator (width × height ÷ 144), a rough-opening calculator (unit size + shim gaps), an egress window size & compliance checker (labeled IRC R310), a window count / quantity calculator, a window-to-wall ratio, and a standard vs custom size reference. Measure each opening (smallest of three) and confirm sizes against the exact product; egress values are labeled code minimums, not a certified sign-off.
Measure each opening and confirm sizes and clearances against the exact product you buy. Take three width and three height measurements and use the smallest of each; allow extra for custom sizes and waste. Sizes, clearances and rough-opening allowances vary by product and brand — read the spec sheet and the manufacturer’s data.
Typical published planning values / code minimums — NOT a certified design or a compliance sign-off. Actual egress compliance and energy performance depend on your local building code (AHJ), climate zone, the exact product’s NFRC-rated U-factor & SHGC and the installation; confirm against local code and the manufacturer’s NFRC label, and consult a pro. Structural headers for enlarged openings, whole-building heat-load / HVAC sizing and code certification are set by code and a professional — not engineered here.
United-inches calculatorAdd width + height to get your window's united inches (UI) — the size number suppliers use to price windows. Free calculator, formula and common-size chart.Window area (square footage)Convert window width and height (inches) to glass area in square feet: width × height ÷ 144. Worked example, a size chart and the frame-vs-daylight difference.Rough-opening calculatorSize the rough opening for a window: unit size plus a shim gap per side (typically ½ in). Worked example, a shim-gap chart and why to confirm the spec sheet.Egress window checkerCheck a window against the IRC R310 egress minimums: 5.7 sq ft clear opening, 20 in wide, 24 in tall, 44 in max sill. Screens each test and explains why.Window count calculatorCount the windows in a house room by room to get the total openings to order and budget. Worked example, a windows-by-home-size chart and how to count bays.Window-to-wall ratio (WWR)Calculate window-to-wall ratio (WWR) from total window area and gross wall area. Worked example, typical US ranges and why WWR is a planning figure, not code.Standard vs custom sizeCheck whether a window size is common stock or custom: a labeled stock-size chart, why replacements are usually custom, and the cost and lead-time impact. Every Window Sizing & Quantity tool is calculated server-side — visible immediately — with its formula, a worked example and a reference table, and works on the measurements you take and the prices you enter from your own quotes. Background reading is in the guides.
If you want the sizes as a table rather than a calculation, the rough opening chart for window & door sizes lists the usual shim allowances, and the united-inches sizing convention gives UI for the common stock sizes. A bedroom egress opening below grade also needs a well and a removable cover — those sizes are in the window well cover size guide.