Enter values into the two yellow fields - the rest will be calculated automatically.
If you change a value in the field, all the marked ones recalculate accordingly.
Using the checkbox you can choose any three fields,
that you want to calculate.
For decimals you can enter either points or commas.


a = m
b = m
u = m
O = m
P = m²
α = º
to 6 digits

The result will be in the units that you enter into the fields.
For example, if you enter decimeters, the result will also be in decimeters.

If a NaN error occurs,
you have probably entered invalid values.


    O  = 2 × (a + b) [m]
    P  = a × b [m²]
    u  = a² + b² [m]
tg α  = b / a [º]
+ reverse formulas
Rectangle formula

a … side a length

b … side b length

u … diagonal

α … angle

Rectangle and circle

Diagonal (u) = diameter of a circle circumscribing a rectangle
shorter side of the rectangle (a) = diameter of a circle inscribing a rectangle

For more formulas for circumscribed or inscribed circles, see either this online calculator for circle calculation, or in encyclopedia Wikina under the article about circles here: Circle.

Other formulas are also avaiable on Wikina under the Rectangle keyword.

Online rectangle calculation

Calculator for calculating rectangle's surface, converting the perimeter of a rectangle, rectangle formulas. Calculation of a diameter of a circle circumscribing or inscribing a rectangle, calculation of surface from perimeter. Calculation of rectangle's perimeter online. Rectangle formulas.

Rectangle calculator


How to calculate ...

Bold shapes and objects are already in operation. The others contain only a formula.

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