To measure for replacement windows, measure the width across the top, middle, and bottom of the window opening. Then, measure the height from the top of the sill to the top of the opening on the left, middle, and right. Use the smallest measurements for accuracy, and make sure to measure both the interior and exterior dimensions to ensure a proper fit.

Accurate measurements are essential for replacement windows. Taking multiple measurements for width and height ensures a proper fit. It's important to measure at different points, using the smallest dimension to avoid ordering a window that's too large. Precise measurements result in a tighter fit and better insulation for your home.