How to use this calculator
Calculate key rectangle metrics from length and width.
How the calculation works
- Enter length and width.
- Area and perimeter are calculated directly.
- Diagonal uses the Pythagorean theorem.
Formula
Area = length x width. Perimeter = 2(length + width). Diagonal = sqrt(length² + width²).
Example
A 3 by 4 rectangle has area 12, perimeter 14, and diagonal 5.
Understanding your result
Use the output as a practical starting point, then review it before using it in an important workflow.
Assumptions and limitations
- Use consistent units for length and width.
- For room or project measurements, Construction & DIY tools may be useful.
Frequently asked questions
Does this require an account?
No. The core tool works without creating a Tool2Do account.
Is my input included in share links or analytics?
No. Tool2Do share actions use the tool page URL and safe metadata, not private values or uploaded files.