Little Wonder WorldAn answer you need. A discovery you didn’t expect.
Standard order of operations; brackets first. % always means divide by 100: 100 + 10% = 100.1. For discounts or increases, use the percentage tool. ≈ means rounded to 12 decimal places.
Up to 15 calculations, kept only while this page stays open.
Percentage change divides by the absolute original value; it is undefined when that value is zero.
Looking for an octagon? Open the dedicated octagon area calculator →
A room, a garden, an eight-sided gazebo—or an outline all your own. Choose a shape, add your measurements and discover its area.
Results are rounded to 10 significant figures. Changing units converts your existing dimensions and coordinates, preserving the physical size.
Tap or click anywhere along an edge to add a point, then drag it. Drawing grid: x = 0–20, y = 0–13. For larger or more precise plots, type coordinates. Keyboard users can edit every corner in the coordinate field.
Use matching units for every dimension. A radius is half the diameter; an ellipse uses two radii. A perpendicular height is measured at 90° to the base.
For an irregular plot, enter each corner in order around its boundary. Concave shapes work too. For holes or curved boundaries, calculate separate pieces and add or subtract their areas using the everyday calculator above.
Side lengths alone don’t determine the area of an irregular polygon. Custom mode therefore uses corner coordinates. This calculator measures flat, two-dimensional shapes; it does not calculate 3D surface areas.
Find an interval, move a date, or work out what time it will be.
Device time zone: . Both endpoints use that same zone in elapsed-time mode. Repeated or nonexistent times at clock changes are rejected. Leap seconds are excluded; duration days mean 24 hours. Dates are interpreted using the Gregorian calendar.
Use a negative adjustment to subtract. Years 0100–9999 supported.
For seconds, minutes, hours, days and weeks, use the duration converter above ↑.
Arithmetic uses exact fractions internally. Displayed answers are rounded to a maximum of 12 decimal places, with ≈ where rounding changes the value. Scientific notation such as 1e6 is accepted; exponents are limited to −30 through 30. Very large expressions are rejected to keep the calculator responsive. There is no implicit multiplication: write 2 × (3 + 4).
All calculations run on your device. Inputs and history are not stored by these tools or included in links. Hosting processes ordinary page requests. Mathematical discoveries refer to the underlying value; approximate comparisons are labelled. Refreshing the page clears history.
Calendar arithmetic differs from actual elapsed time. A calendar month has a variable length; a duration day is defined here as 24 hours. Actual elapsed times depend on the device time zone and the browser’s time-zone data. This is not a historical calendar-conversion service.
Discover your life in numbers → · Take a little game break →
Play today’s free Sudoku in easy, medium or hard mode. Progress saves on this device, so you can leave and come back. Missed a day? Explore the puzzle archive.
Curious about a personal milestone? Explore your birthday in numbers and read how a billion-second birthday is calculated.
A changing pick from our journal: surprising facts and practical ways to explore your world.
A billion sounds impossibly large. In seconds, it is a milestone you can reach in an ordinary lifetime.
Published 26 October 2026 · Sources included
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Seven days in a week, 365 in most years: the tiny mismatch that keeps moving your birthday.
Published 26 October 2026 · Sources included
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Laser measurements reveal a slow change in the average Earth–Moon distance. Your lifetime gives that change a surprising scale.
Published 26 October 2026 · Sources included
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Begin with one address, a local archive and a question small enough to answer. A practical first visit to local history.
Published 26 October 2026 · Sources included
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The hour repeated, the day did not gain extra sunlight, and some household timers may still need checking.
Published 26 October 2026 · Sources included
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A huge personal comparison becomes more interesting when you know which parts are estimates and which are projections.
Published 26 October 2026 · Sources included
Read this little wonder →
