Math quick reference
The formulas that come up most in algebra and geometry classes, plus the conversions everyone forgets.
Algebra
| Name | Formula |
|---|
| Quadratic formula | x = (-b ± √(b² - 4ac)) / 2a |
| Slope | m = (y₂ - y₁) / (x₂ - x₁) |
| Slope-intercept form | y = mx + b |
| Point-slope form | y - y₁ = m(x - x₁) |
| Difference of squares | a² - b² = (a - b)(a + b) |
Geometry
| Shape | Area | Perimeter / Circumference |
|---|
| Rectangle | l × w | 2(l + w) |
| Triangle | ½ b × h | sum of sides |
| Circle | πr² | 2πr |
| Trapezoid | ½(b₁ + b₂) × h | sum of sides |
Pythagorean theorem: a² + b² = c² (right triangles only, c is the hypotenuse).
Unit conversions
| From | To | Multiply by |
|---|
| Inches | Centimeters | 2.54 |
| Miles | Kilometers | 1.609 |
| Pounds | Kilograms | 0.4536 |
| Fahrenheit | Celsius | (°F - 32) × 5/9 |