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Area calculator

Add areas of rectangular, circular and triangular parts to measure a compound surface.

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Area calculator processes your input in this browser. Inputs and results are excluded from analytics. Recent tools save tool names, visit counts and last-visit times. Saved tools store only their names. Draft saving is optional and stays on this device; delete saved text with the draft controls. Loading text from a URL is optional and contacts that server; its URL and your IP address are visible to the server. An optional “Use in” action keeps a handoff in this tab. The next tool removes it on arrival and ignores it if more than a minute has passed.

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Answer

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Add areas of rectangular, circular and triangular parts to measure a compound surface.

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Precision and calculation record
Rounding changes displayed numbers, not the calculation. Text, fractions, matrices and CSV schedules keep their own formatting. Automatic keeps up to 12 significant digits, with money shown to cents where applicable.
Saved scenario
Save the current answer, then change an input to compare. This clears when you leave.
Formula and assumptions
Rectangle = length × width; circle = πr²; triangle = base × perpendicular height/2. Put one shape per line or separate with semicolons. Use one unit and nonoverlapping parts; overlapping areas are not automatically removed. Select Feet to also report building-material squares, each defined as 100 square feet. Separate dimensions with spaces; 1,000 is a single dimension value.
Automatic precision shows numbers to 12 significant digits. Thousands separators such as 1,000 are accepted; use a dot for decimals.
Scratch calculator
Use +, −, ×, ÷, parentheses and %. A percentage is divided by 100. This does not change the main tool.
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Updated 
Using Area calculator
Add areas of rectangular, circular and triangular parts to measure a compound surface.
Rectangle = length × width; circle = πr²; triangle = base × perpendicular height/2. Put one shape per line or separate with semicolons. Use one unit and nonoverlapping parts; overlapping areas are not automatically removed. Select Feet to also report building-material squares, each defined as 100 square feet.
Next: Rectangle calculator
Next: Perimeter calculator
A worked example
Example inputs: parts: rectangle length width; circle radius; triangle base height = rectangle 4 3; circle 2. Total area = 24.5663706144.
Before you use the result
Rectangle = length × width; circle = πr²; triangle = base × perpendicular height/2. Put one shape per line or separate with semicolons. Use one unit and nonoverlapping parts; overlapping areas are not automatically removed.
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ToolOctopus. “Area calculator.” Updated 2026-09-26. https://tooloctopus.com/area-calculator.
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