United-inches calculator
Add a window’s width and height in inches to get its united inches — the single number suppliers use to size and price a window.
A 36 × 60 inch window is 96 united inches (UI = width + height). Suppliers quote and price windows by UI, and it is the single number that lets you compare a tall casement to a wide slider. Measure to the frame and use the smallest of three widths and three heights.
Calculator inputs
United inches (UI) is the fenestration trade’s master size. Instead of quoting a width and a height separately, a supplier adds them into one number: a 36 × 60 inch window is 96 united inches. Because a tall casement and a wide slider with the same UI use roughly the same amount of frame and glass, UI is how price lists, size charts and shipping tiers are organized — and it is the fastest way to compare two windows that aren’t the same shape.
Measure to the frame (the outside of the window unit), not the glass, and take the smallest of three width and three height readings so an out-of-square opening doesn’t leave you short. The calculator also returns the glass/daylight area as a cross-check.
Formula
united_inches = width_in + height_in
It really is that simple — UI is a sum, not a product, so it is not an area. (Area is width × height ÷ 144; the tool shows that too, so you can carry both numbers to the supplier.)
Worked example
Take a common 36 × 60 inch double-hung window:
united_inches = 36 + 60 = 96 united inches
Its glass area is 36 × 60 ÷ 144 = 15.0 sq ft. So you would order it as a “96 UI” window and expect about 15 square feet of glass. A 40 × 56 inch casement is also 96 UI — same size tier, different proportions.
What to measure first & common mistakes
- Frame, not glass. UI uses the window unit’s outside width and height. The visible glass (daylight opening) is smaller — use it only where a spec sheet explicitly calls for daylight dimensions.
- Smallest of three. Measure width at top, middle and bottom, height at left, center and right, and use the smallest of each. Old openings are rarely square.
- UI is not area and not the rough opening. It is a sizing/pricing index. For the framed hole, use the rough-opening calculator; for glass area, the window area calculator.
- Round to the supplier’s increments. Many lines size in whole or half inches; a fractional measurement usually means a custom order.
Reference table
Common nominal window sizes and their united inches (labeled planning sizes — confirm availability with the supplier).
| Nominal size | United inches | Glass area |
|---|---|---|
| 24 × 36 in | 60 UI | 6.0 sq ft |
| 24 × 48 in | 72 UI | 8.0 sq ft |
| 28 × 54 in | 82 UI | 10.5 sq ft |
| 30 × 36 in | 66 UI | 7.5 sq ft |
| 30 × 48 in | 78 UI | 10.0 sq ft |
| 30 × 60 in | 90 UI | 12.5 sq ft |
| 32 × 48 in | 80 UI | 10.7 sq ft |
| 32 × 54 in | 86 UI | 12.0 sq ft |
| 36 × 48 in | 84 UI | 12.0 sq ft |
| 36 × 54 in | 90 UI | 13.5 sq ft |
| 36 × 60 in | 96 UI | 15.0 sq ft |
| 36 × 72 in | 108 UI | 18.0 sq ft |
| 48 × 48 in | 96 UI | 16.0 sq ft |
| 48 × 60 in | 108 UI | 20.0 sq ft |
| 60 × 48 in | 108 UI | 20.0 sq ft |
| 72 × 60 in | 132 UI | 30.0 sq ft |