🧮 Math
Equation Solver
Use this free equation solver to get fast, accurate results.
📝 Your Assumptions
The Equation Solver gives you the result of any percentage-based equation in one step. Enter a value and a percentage, and it returns the exact number instantly. Use it for markups, discounts, tips, taxes, and interest to avoid manual math errors.
How to Use This Calculator
Follow these five steps to get an accurate result every time.
1
Enter the base value
Type the starting number into the Value field. For example, enter 250 if you are calculating 15% of $250.
2
Enter the percentage
Type the percentage into the Percentage field without the % sign. For 15%, enter 15.
3
Click calculate
Press the Calculate button to run the percentage engine. The result appears immediately below.
4
Check the result
The output shows the computed number, such as 37.5 for 15% of 250. Verify it matches your expectation.
5
Adjust and recalculate
Change either input and calculate again. For instance, switch 15% to 20% to see 250 become 50.
What Your Results Mean
Each result reflects the percentage relationship between your two inputs.
Direct percentage result
The output is the percentage of the value you entered. For 80 and 25%, the result is 20.
Decimal conversion
The calculator converts the percentage to a decimal by dividing by 100. So 7.5% becomes 0.075 before multiplying.
Scaling with value
Doubling the value doubles the result. If 10% of 50 is 5, then 10% of 100 is 10.
Scaling with percentage
Doubling the percentage doubles the result. If 5% of 200 is 10, then 10% of 200 is 20.
Common use: discounts
A 30% discount on $120 gives a result of $36 off. Subtract that from $120 to pay $84.
Common use: tips
A 20% tip on an $85 bill is $17. Add it to the bill for a total of $102.
Key Terms
Percentage
A number expressed as a fraction of 100. For example, 25% means 25 out of 100.
Base value
The starting number you apply the percentage to. In 15% of 200, 200 is the base value.
Decimal
A number written with a point, such as 0.15, which is equivalent to 15%.
Markup
The amount added to a cost to set a selling price. A 40% markup on $50 adds $20.
Discount
A reduction from the original price. A 10% discount on $75 removes $7.50.
❓ Frequently Asked Questions
Multiply the number by the percentage divided by 100. For example, to find 18% of 250, convert 18% to 0.18 and multiply: 250 × 0.18 = 45. The Equation Solver does this automatically when you enter 250 as the value and 18 as the percentage. If you need to find what percentage one number is of another, use the percentage calculator on this site. For changes between two numbers, the percentage change calculator gives the increase or decrease.
They mean the same thing. Percent means 'per hundred,' and percentage is the result of that calculation. For instance, 20 percent and 20% are identical. In the Equation Solver, you enter 20 in the Percentage field for either term. If you are comparing two values, such as 30 and 150, the percentage is 20% because 30 ÷ 150 = 0.20. The percentage change calculator helps when you need the difference between an old and new value, like 150 to 180, which is a 20% increase.
First find the percentage of the number, then add or subtract it. For a 12% sales tax on a $60 purchase, 12% of 60 is 7.20, so the total is $67.20. For a 25% discount on $80, 25% of 80 is 20, so you pay $60. The Equation Solver gives you the percentage amount, and you do the final addition or subtraction. For direct increase or decrease, the percentage increase calculator handles it in one step.
Yes. Enter the bill amount as the value and the tip percentage as the percentage. A 22% tip on a $95 bill is 95 × 0.22 = $20.90. If you want to split the total among 4 people, add the tip to the bill ($115.90) and divide by 4 to get $28.98 each. For a quick check, a 20% tip on $50 is $10. The percentage calculator can also help you find what percent one number is of another, like what percent $20.90 is of $95.
The Equation Solver finds a percentage of a single value, such as 15% of 200 = 30. The percentage change calculator compares two values to find the increase or decrease between them. For example, if a stock goes from $40 to $50, the percentage change is 25% because (50 − 40) ÷ 40 = 0.25. Use the Equation Solver when you have a base and a rate; use the percentage change calculator when you have an old and new number.
The most common error is forgetting to divide by 100. Entering 8% as 8 instead of 0.08 gives a result 100 times too large. Another mistake is applying a percentage to the wrong base. For a 30% discount on a $120 item, the discount is $36, and the final price is $84—not $36. Also, adding 10% and then subtracting 10% does not return the original number: $100 + 10% = $110, then $110 − 10% = $99. Always double-check your base value. The percentage increase calculator can verify changes step by step.
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