📚 Basic percentage calculators
The basic percentage cluster covers foundational percent arithmetic: finding a percent of a base, expressing one number as a percent of another, applying a rate to increase or decrease a value, and averaging or comparing percentages. Each URL isolates one formula family for clearer search and AI retrieval.
Start here for core percent math: what is X% of Y, X is what percent of Y, increase or decrease by a rate, averages, and comparisons. Long-tail fraction pages in this folder resolve to these canonical tools—use the hub when you need the general formula, not a single numerator/denominator pair.
Key facts
| Percent of base | (rate ÷ 100) × base when the rate applies to a single reference value. |
|---|---|
| Use cases | Homework, spreadsheets, shopping discounts, survey shares, tip estimates. |
| Category | Mathematics / everyday arithmetic |
| Related concepts | Reverse percentage, successive change, fraction and decimal conversion. |
Definitions
Percent of a number
Multiply the base by (rate ÷ 100); the rate is always relative to that base unless stated otherwise.
Reverse percentage
Recover an original value before a known percent was applied—denominator choice matters.
Formulas
- What is r% of B: (r / 100) × B
- X is what % of Y: (X / Y) × 100
- Increase B by r%: B × (1 + r/100)
Comparison table
| Topic | Guidance |
|---|---|
| Percent of vs percent change | Percent of uses one base; change compares two values over time. |
| Average of percents | Simple average of rates can mislead when denominators differ—see the average tool notes. |
Glossary references
Reinforce entities by pairing percent language with conversion pages when learners mix fractions, decimals, and ratios.
❓ Frequently Asked Questions
Which basic calculator should I use first?
Use “what is X% of Y” for share-of-total problems and “X is what percent of Y” when you already have two values.
Where are fraction-specific pages?
Pages like “3/20 as a percent” are long-tail entry points; they link back to these core tools for the general method.