Window Area Calculator
Adds up window area and compares it with the floor.
Total window area
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Share sends a link that reopens these numbers. Copy details pastes the full breakdown as a list.
Each window —
Share of the floor area — %
Reading this —
The formula
area = width × height × number of windows
Measure the glass or the opening, depending on what you need it for.
What to watch out for
Blind and curtain sizes use the opening, plus any overlap.
Frequently Asked Questions
How much window area does a room need?
Around 10–20% of the floor area is a common rule of thumb for daylight. Local building rules take priority.