Calculators

Percentage Calculator

Calculate percentages, percentage change, and what percent one number is of another.

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Percentage (%)

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About Percentage Calculator

The Automarkly Percentage Calculator is a versatile and free online tool that solves the three most common percentage problems in an instant. Whether you need to find a percentage of a number, calculate the percentage increase or decrease between two values, or determine what percentage one number represents of another, this tool has you covered. Percentages are everywhere — in discounts, taxes, tips, grades, interest rates, growth metrics and data analysis — and this calculator removes the guesswork from all of them.

Calculating percentages by hand is a frequent source of errors, especially when dealing with percentage change, where the direction (increase vs decrease) and the base value both matter. Our tool uses precise arithmetic and clearly labels each input so you always know exactly what is being calculated. Switch between three modes with a single tap: 'X% of Y' for basic percentage calculations, '% Change' for increase or decrease between two values, and 'X is what % of Y' for proportion calculations.

Worked examples: (1) X% of Y — 15% of 80 = (15/100) × 80 = 12. (2) % Change — going from $200 to $250 is ((250−200)/|200|) × 100 = +25% increase; going from $250 back to $200 is ((200−250)/|250|) × 100 = −20% decrease. (3) X is what % of Y — 30 is what % of 150 = (30/150) × 100 = 20%.

This calculator is designed for real-world use. Shoppers can quickly work out the final price after a discount. Students can verify their exam percentage. Business owners can calculate revenue growth quarter over quarter. Investors can figure out the return on an investment. Marketers can determine conversion rates. Each mode is self-explanatory, and the result updates in real time as you type — no need to press a calculate button.

Like all Automarkly tools, the Percentage Calculator runs entirely in your browser. Your inputs are never sent to a server, there are no accounts to create, and the tool is completely free with no usage limits. It works flawlessly on desktop and mobile, making it easy to pull up whenever you need a quick, reliable percentage calculation.

How to Use Percentage Calculator

Select the calculation mode you need at the top.

For 'X% of Y': enter the percentage and the value.

For '% Change': enter the original and new values.

For 'X is what % of Y': enter the part and the whole.

Read the instant result displayed below the inputs.

Key Benefits

Three calculation modes in one tool.

Handles percentage increase and decrease with sign indicators.

Real-time results — updates as you type.

Perfect for discounts, grades, tips, taxes and growth metrics.

100% client-side — your numbers never leave your browser.

Free, no sign-up, works on all devices.

Common Use Cases

Calculating a sale discount: a $120 item at 30% off saves $36 (30% of 120), so the sale price is $84.

Figuring out a tip: 18% tip on a $45 restaurant bill = (18/100) × 45 = $8.10.

Checking exam scores: if you scored 42 out of 50, your percentage is (42/50) × 100 = 84%.

Measuring business growth: revenue going from $50,000 to $62,000 QoQ is ((62,000−50,000)/50,000) × 100 = +24% growth.

Calculating conversion rates: if 120 out of 3,000 visitors bought a product, (120/3,000) × 100 = 4% conversion rate.

Determining market share: if your company has $2M revenue in a $15M market, (2/15) × 100 = 13.3% market share.

Frequently Asked Questions

How do I calculate a percentage of a number?

Use the 'X% of Y' mode. Enter the percentage (e.g., 20) and the value (e.g., 150). The result (30) is 20% of 150.

How is percentage change calculated?

Percentage change = ((new value − original value) / |original value|) × 100. A positive result indicates an increase; a negative result indicates a decrease.

Can I calculate a discount with this tool?

Yes. To find the discount amount, use 'X% of Y' with the discount percentage and original price. To find the sale price, subtract the result from the original price.

What does 'X is what % of Y' mean?

It finds the proportion of X relative to Y as a percentage. For example, 25 is what % of 200 gives 12.5%.

Is this tool free to use?

Yes, the Automarkly Percentage Calculator is completely free, requires no sign-up, and has no usage limits.

Why isn't percentage change symmetric?

Because the base (denominator) changes. Going from 100 to 150 is +50% (base is 100), but going from 150 back to 100 is −33.3% (base is 150). The same absolute change (50) produces different percentages depending on the starting value.

Can I use this for compound percentage changes?

This tool calculates single-step percentage change. For compound changes (e.g., 10% growth then 5% decline), calculate each step separately or use our Compound Interest Calculator for multi-period growth.

Does the tool handle negative numbers?

Yes. You can enter negative values. For percentage change, the tool uses the absolute value of the original number as the denominator, so the sign of the result correctly reflects increase (+) or decrease (−).

Tips & Best Practices

When calculating percentage change, always use the original (starting) value as the denominator, not the new value.

A percentage increase from 100 to 150 is +50%, but a decrease from 150 back to 100 is -33.3% — the direction matters.

For discounts, calculate the discount amount first, then subtract from the original price to get the sale price.

When comparing growth rates, use percentage change rather than absolute differences for meaningful comparisons.

Remember that a 100% increase doubles a value, while a 50% decrease only brings it back down by half — increases and decreases aren't symmetric.

Use the 'X is what % of Y' mode to calculate conversion rates, test scores, or market share.

Conclusion

The Percentage Calculator handles the three most common percentage calculations instantly — finding a percentage of a number, calculating percentage change, and determining what percentage one value is of another. Whether you're shopping, studying, analyzing business growth, or working with data, this tool delivers accurate results in real time. Explore our related math and financial calculators for more resources.

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