Calculator Inputs
Choose a mode, enter values, and calculate instantly.
Formula Used
Basic percentage
Amount = Base × (Percent ÷ 100)
Part to percent
Percent = (Part ÷ Whole) × 100
Original from percent
Original = Known Value ÷ (Percent ÷ 100)
Percentage change
((New − Old) ÷ Old) × 100
Proportion solving
If A:B = C:X, then X = (B × C) ÷ A
Direct and inverse proportion
Direct uses a constant ratio. Inverse uses a constant product.
How to Use This Calculator
- Choose the correct calculation mode for your problem.
- Enter the known values in the visible fields.
- Set decimal places for the output you want.
- Press Calculate to show the result above the form.
- Use the CSV or PDF buttons to save the result summary.
Example Data Table
| Scenario | Inputs | Output |
|---|---|---|
| Percentage of value | Base = 250, Percent = 18 | 45 |
| Part of whole | Part = 45, Whole = 60 | 75% |
| Original from percent | Known value = 72, Known percent = 24% | 300 |
| Percentage change | Old = 120, New = 150 | 25% |
| Solve proportion | 4 : 9 = 12 : X | 27 |
| Ratio distribution | Total = 5,000, Ratio = 2:3:5 | 1,000 | 1,500 | 2,500 |
Frequently Asked Questions
1. What does this calculator solve?
It solves common percentage and proportion problems, including percent of a value, unknown percentages, percentage change, direct proportion, inverse proportion, and ratio-based splitting.
2. When should I use direct proportion?
Use direct proportion when two values increase or decrease together at a constant rate, such as price by quantity or distance by time at fixed speed.
3. When should I use inverse proportion?
Use inverse proportion when one value rises while the other falls so their product stays constant, such as workers and completion time.
4. Can I use decimals and negative values?
Yes. Decimal inputs are supported in every mode. Negative values also work where mathematically meaningful, except ratio terms, which must stay positive for valid distribution.
5. Why is percentage change sometimes negative?
A negative percentage change means the ending value is lower than the starting value. The sign helps distinguish decreases from increases clearly.
6. What format should ratio terms use?
Enter ratio terms like 2:3:5. You can also separate terms with spaces, commas, or hyphens. All terms must be numeric and greater than zero.
7. What do the CSV and PDF buttons export?
They export the visible result summary table after calculation. That makes it easy to save your work, attach it to notes, or share it later.
8. Is this calculator suitable for classroom use?
Yes. It works well for homework, worksheets, quick checks, estimation practice, and step verification because it shows formulas and a worked calculation line.