Area Converter

Convert square metres, square feet, acres and hectares — ten area units, worked out in this browser tab.

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What this tool does

Area Converter carries ten units: square millimetre, square centimetre, square metre, hectare, square kilometre, square inch, square foot, square yard, acre and square mile. Each one is stored as a fixed ratio to the square metre, so converting is a single multiplication and division rather than a lookup in a pre-rounded table, and any pair of units in the list works in either direction.

Input is one value per line. A bare number uses the From and To menus; a unit typed after the number, such as 1500 sq ft, replaces the From menu for that line; a to clause, as in 1 ha to acres, replaces the To menu. Spelling is matched loosely, so sq ft, sq. ft, sqft, ft², square foot and square feet all reach the same unit, and m2, cm2, in2, yd2, km2 and mi2 are accepted as plain-ASCII spellings. Numbers are read the way people actually write them — 1,234 and 1'234 are treated as thousands separators, 1.234,5 is read as a Continental decimal, and 1 1/2 and 1½ both parse as one and a half.

Results appear as a two-column table, the input beside the result, with a summary line underneath carrying the factor for the last pair converted — 1 ft² = 0.09290304 m². Precision defaults to Automatic, which keeps ten significant digits and trims the trailing zeros, dropping to eight once a result is far enough from 1 to be written in exponential form. The fixed settings are 0, 1, 2, 3, 4, 6 or 8 decimals, which is what makes a column of quoted figures line up. Set To to All units (table) and one value is expanded into every unit at once — that view has no single pair to name, so the factor drops out of the summary — and Copy output hands back the whole table as CSV.

Three things it will not do are worth knowing before a figure goes anywhere binding. It converts area units and does not work an area out from dimensions, so a room typed as 12 ft x 10 ft is refused — multiply the sides yourself and convert the product. The one spelling it mishandles is ft2 written without the superscript: the number parser shared with Length Converter reads it as one foot two inches, and the line is then rejected because feet are not an area unit, so write sq ft or ft² instead. And the acre, foot and mile here are the international definitions, which places one acre at 4046.8564224 m²; American land records still written in US survey feet use an acre about 0.016 m² larger, roughly one part in 250,000 — invisible for a garden, not invisible on a deed.

How to use it

  1. Type the value, or a list of them. Each line is converted in its own right. Load sample fills the box with a bare number, a hectares-to-acres line and a square feet conversion so you can see the three input styles side by side.
  2. Pick From and To, or name the unit in the line. The menus set the default pair. Anything you type after the number wins over the From menu, and anything after "to" wins over the To menu.
  3. Decide how many decimals you want. Automatic keeps ten significant digits and drops trailing zeros. The fixed choices are 0, 1, 2, 3, 4, 6 or 8 decimals — there is no 5 and no 7 — and a fixed setting is what you want when the numbers go into a quote.
  4. Read the table, or take it as CSV. The result table shows every line you entered. Copy output puts it on the clipboard as CSV, ready to paste into a spreadsheet.

Processing & privacy

Runs on your device. Your file is processed directly in this browser.

Common use cases

Comparing two property listings

One agent quotes 1,450 sq ft and the other 135 m². Converting both to the same unit is the only way to see which flat is actually bigger.

Reading a plot of land in the wrong unit

Land is sold in acres in some places and hectares in others. One hectare is 2.471053815 acres, which is the sort of number nobody should be doing on paper.

Ordering materials by coverage

Turf, flooring and paint are sold per square metre while the room was measured in square feet. Convert the total once instead of guessing a margin.

Normalising a pasted column of sizes

Paste hundreds of parcel or floor areas, one per line, set the pair once, and copy the converted table straight back into the spreadsheet.

Questions

Is anything I type sent to a server?
No. The unit table ships with the page and the arithmetic happens in this tab, so nothing is transmitted or stored, and once the page has loaded, pulling out the network does not stop it converting.
Can it work out the area of a room from its length and width?
No. It converts a single area value, so 12 ft x 10 ft is not accepted as input. Multiply the sides first — 120 — then convert that number from square feet.
Why does 1500 ft2 fail when 1500 sq ft works?
Because ft2 is caught by the feet-and-inches reader this converter shares with Length Converter, which turns it into 1500 feet 2 inches. Feet are not an area unit, so the line is then refused with an unknown-unit error naming ft. Write sq ft, sqft or ft²; the ASCII forms m2, cm2, in2, yd2, km2 and mi2 have no such clash and work as typed.
Which acre and which square mile does it use?
The international ones, built on the international foot of exactly 0.3048 m: 4046.8564224 m² to the acre and 2589988.110336 m² to the square mile. It has no separate US survey values, so a US deed measured in survey feet will differ in about the sixth significant digit.
Does it know bigha, cent, marla, dunam or tsubo?
No. The list is the ten metric and imperial units named on this page, so regional land measures — which often vary by district anyway — are not covered and cannot be typed as a unit. The are and the rood are missing for the same reason.
Why is my answer written as 3.8610216e-13?
Because the number is smaller than a millionth. Automatic precision switches to exponential notation below 1e-6, and again from 1e15 upwards, rather than printing a long run of zeros; the exponential form carries eight significant digits. Choosing a fixed number of decimals gives the plain form.
How many values can I convert at once?
As many lines as you care to paste. Long lists are processed in batches so the tab stays responsive, and every line lands in the same output table.
What happens if I mistype a unit?
The whole conversion stops and names the problem: an unrecognised unit is quoted back with the first eight area symbols offered as suggestions, and a line that does not begin with a number is reported by its line number.

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