How to measure a window for replacement — three widths, three heights, use the smallest

Measure width at top, middle, and bottom and height at left, center, and right, then use the smallest of each — openings are rarely square. Insert units measure to the existing frame; full-frame measures to the rough opening.

An inside elevation of a window showing the replacement-measurement method. The width is measured at three places — top, middle, and bottom — and the height at three places — left, center, and right — because an old opening is rarely perfectly square. You order to the smallest of the three widths and the smallest of the three heights so the new unit fits. An inset notes the two paths: an insert (pocket) replacement is measured to the inside of the existing frame, which stays in place, while a full-frame replacement is measured to the rough opening after the old frame is removed. — Source: Manufacturer replacement-measurement practice (insert vs. full-frame)

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An inside elevation of a window showing the replacement-measurement method. The width is measured at three places — top, middle, and bottom — and the height at three places — left, center, and right — because an old opening is rarely perfectly square. You order to the smallest of the three widths and the smallest of the three heights so the new unit fits. An inset notes the two paths: an insert (pocket) replacement is measured to the inside of the existing frame, which stays in place, while a full-frame replacement is measured to the rough opening after the old frame is removed.

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    Diagram: <a href="https://remodelcalculators.com/construction-diagrams/window-measure-replacement" target="_blank" rel="noopener">How to measure a window for replacement — three widths, three heights, use the smallest</a> — courtesy of <a href="https://remodelcalculators.com" target="_blank" rel="noopener">RemodelCalculators.com</a>
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