To find the area of a rectangle, multiply its length by its width: Area=length×width\text{Area}=\text{length}\times \text{width}Area=length×width.

What “area of a rectangle” means

Area tells you how much space is inside the rectangle’s boundary.

If you imagine the rectangle made of 1-by-1 little squares, the area is how many of those squares fit inside.

The core formula (super quick)

For any rectangle:

Area=length×width\text{Area}=\text{length}\times \text{width}Area=length×width

  • Length: one side (usually the longer side).
  • Width (or breadth): the side next to it.
  • Units: if sides are in cm, area is in square cm (cm²); if in m, area is in m².

Example:
A rectangle is 5 cm long and 6 cm wide.
Area = 5 × 6 = 30 cm².

Step‑by‑step method

  1. Identify the length and width from the problem or diagram.
  1. Make sure both are in the same unit (both in cm, or both in m, etc.).
  1. Multiply them: length × width.
  1. Attach “square” to the units (cm², m², etc.).

If you know different information

Sometimes you are not given both sides directly but you can still find the area.

1. Using diagonal and one side

If you know:

  • Diagonal ddd
  • One side, say length lll

Then:

  1. Find the other side (width www) using Pythagoras:

w=d2−l2w=\sqrt{d^{2}-l^{2}}w=d2−l2​

2. Then area = l×wl\times wl×w.

Example:
Diagonal 10 units, length 8 units.
Width = 102−82=100−64=36=6\sqrt{10^{2}-8^{2}}=\sqrt{100-64}=\sqrt{36}=6102−82​=100−64​=36​=6.

Area = 8 × 6 = 48 square units.

2. Using perimeter and one side

Perimeter PPP of a rectangle is P=2(l+w)P=2(l+w)P=2(l+w).

If you know the perimeter and one side, you can find the other:

  1. Use P=2(l+w)P=2(l+w)P=2(l+w) to solve for the missing side.
  1. Then multiply length × width for area.

Example:
Perimeter = 30 units, width = 4 units.
From 30=2(l+4)30=2(l+4)30=2(l+4) → l=11l=11l=11 units.

Area = 11 × 4 = 44 square units.

Mini “Quick Scoop” recap

  • Formula: Area of a rectangle = length × width.
  • Both measurements must be in the same unit (like all in cm or all in m).
  • Answer is always in square units (cm², m², etc.).
  • If you only know diagonal + one side or perimeter + one side, you can first find the missing side, then use the same formula.

If you send a specific rectangle (like “length 12 cm, width 7 cm”), I can walk through the exact calculation for that example.

Information gathered from public forums or data available on the internet and portrayed here.