Percentage Increase: 5 Mistakes to Avoid
Adds a percentage to a number. The maths is not complicated, but a handful of errors come up again and again in this and related math & geometry calculations. Here is what to watch for.
Rounding is a common source of small errors. Keep full precision during intermediate steps and round only the final answer to the number of decimal places or significant figures the question asks for.
These calculations appear throughout the Singapore syllabus, from primary school percentages and fractions to secondary school algebra and geometry. Understanding the formula makes problem sums easier because you can recognise which quantity is missing.
1. Using the wrong percentage base
A percentage change is measured against the original value, not the new one.
2. Confusing radius and diameter
Many circle formulas use the radius, which is half the diameter.
3. Population versus sample formulas
Sample standard deviation divides by n − 1; population divides by n.
4. Mixing units
Measurements must all be in the same unit before applying the formula.
5. Dropping negative signs
Signs matter for roots, changes and differences.
The correct method
New = value × (1 + p/100).
For example, with these inputs:
- Starting value: 250
- Increase (%): 12
the calculator returns:
- New value: 280
- Increase: 30
Related calculations
- Volume of a Square Pyramid Calculator: Calculates the volume of a square pyramid from the measurements you enter.
- Volume of a Hemisphere Calculator: Calculates the volume of a hemisphere from the measurements you enter.
- Surface Area of a Cube Calculator: Calculates the surface area of a cube from the measurements you enter.
- Surface Area of a Cuboid Calculator: Calculates the surface area of a cuboid from the measurements you enter.
The Percentage Increase Calculator applies the formula consistently, so it is a quick way to double-check your own working.
Run your own numbers: Percentage Increase Calculator