Calculate the area of any flat shape.
Choose the shape and enter the dimensions.
This tool is most valuable when you need a result to compare against something else: a quoted figure, a competing option, or a budget threshold. Accurate comparisons require accurate inputs and arithmetic — this calculator ensures both.
A common mistake is applying the formula in the wrong direction — particularly with percentage and ratio problems, where the part and the whole can be mistakenly swapped. Check which value is the reference (the 'whole') before entering inputs.
A shopper sees two versions of the same product at different prices: one at £14.50 for 400g and another at £11.99 for 300g. Running both price-per-gram calculations reveals the larger pack is 7% cheaper per unit — the kind of comparison that is impossible to do reliably in your head at the shelf.
A = π × r², where r is the radius.
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