Isosceles Triangle Calculator

Your details

Choose which two values you know. The calculator derives everything else.
The unequal side between the two equal legs.
cm
Length of each of the two equal sides. Must be greater than half the base.
cm
Area
12cm²
Height (h_b)4cm
Perimeter16cm
Semiperimeter (s)8cm
Equal leg (a)5cm
Base (b)6cm
Apex angle (A)73.74°
Base angle (B)53.13°
Altitude to leg (h_a)4.8cm
Inradius (r)1.5cm
Circumradius (R)3.125cm

Area: 12 cm², height: 4 cm.

  • The perimeter is 16 cm, split as two legs of 5 cm and a base of 6 cm.
  • The apex angle is 73.7° and each base angle is 53.1°. All three sum to 180°.
  • The inscribed circle (inradius) has a radius of 1.5 cm; the circumscribed circle (circumradius) has a radius of 3.125 cm.

Next stepFor a triangle with three different side lengths, use the general triangle calculator with Heron's formula.

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