If the length of the hypotenuse is 'h' units and the lengths of the other two sides are 'l', then the perimeter of an isosceles right triangle would be: Perimeter of isosceles right triangle = h + l + l. Since it is a right-angled triangle, one of its sides is the hypotenuse and the other two sides are equal.
The perimeter of an isosceles right-angled triangle can be found by adding the length of all its three sides.
