Frequently Asked Questions

Quick answers to the 60 questions people ask most about percentages, profit and loss, conversions and this site. Each group links to the matching tool and guide.

Percentage and discount

What is a percentage?

A percentage is a number out of 100. So 25% means 25 out of every 100, or one quarter. It lets you compare parts of different wholes on the same scale. Our guide on how to calculate percentage and discount explains it with examples.

How do I find a percentage of a number?

Multiply the number by the percentage and divide by 100. For example, 15% of 200 is 200 × 15 ÷ 100 = 30. The percentage calculator does this in one step.

How do I calculate a discount?

Multiply the original price by the discount percentage and divide by 100 to get the amount saved, then subtract it from the price. A 25% discount on 80 saves 20, so you pay 60.

What is the fastest way to get a sale price?

Multiply the price by what remains after the discount. If the discount is 25%, 75% remains, so the sale price of an 80 item is 80 × 0.75 = 60. This is one step instead of two.

How do I add tax, a service charge or a tip?

Work out the percentage of the amount and add it on. A bill of 50 plus 5% tax is 50 + 2.50 = 52.50. You can also multiply by 1.05 to get the same total directly.

How do I find the original price before a discount?

Divide the sale price by the share that remains. If a coat costs 90 after 25% off, the 90 is 75% of the original, so the original price is 90 ÷ 0.75 = 120. Adding 25% to 90 gives the wrong answer.

Do two discounts add together?

No. Taking 20% off and then 10% off gives 28% off in total, not 30%, because the second discount applies to the already reduced price. Multiply the remaining shares: 0.8 × 0.9 = 0.72.

How do I calculate a percentage increase?

Subtract the old value from the new value, divide by the old value and multiply by 100. A rise from 50 to 60 is (60 − 50) ÷ 50 × 100 = 20%.

How do I calculate a percentage decrease?

Subtract the new value from the old value, divide by the old value and multiply by 100. A fall from 60 to 50 is (60 − 50) ÷ 60 × 100 = 16.7%.

Why does a 10% rise followed by a 10% fall not return to the start?

Because the second percentage applies to a different base. 100 plus 10% is 110, and 10% of 110 is 11, so the fall brings you to 99, not 100.

How do I turn a fraction or decimal into a percentage?

Multiply the decimal by 100. So 0.25 is 25%. For a fraction, divide the top by the bottom first: 3 ÷ 4 = 0.75, which is 75%.

What is the difference between percent and percentage points?

Percentage points describe a plain difference between two percentages. If a rate moves from 10% to 12%, it rises by 2 percentage points, which is a 20% increase in the rate itself.

Can a percentage be more than 100%?

Yes. A percentage above 100% means more than the whole. For example, 150% of 40 is 60. Growth figures often go above 100% when a value more than doubles.

How do I work out what percent one number is of another?

Divide the part by the whole and multiply by 100. If 30 out of 200 people answered yes, that is 30 ÷ 200 × 100 = 15%. You can check results with the percentage calculator.

Profit and loss

How do I calculate profit?

Subtract the cost price from the selling price. If you buy an item for 100 and sell it for 120, the profit is 20.

How do I calculate a loss?

When the selling price is lower than the cost price, subtract the selling price from the cost price. Buying at 100 and selling at 85 is a loss of 15.

How do I calculate profit percentage?

Divide the profit by the cost price and multiply by 100. A profit of 20 on a cost of 100 is 20%. The profit and loss calculator shows the percentage on cost.

What is the difference between margin and markup?

Markup is profit divided by cost. Margin is profit divided by the selling price. A profit of 20 on a cost of 100 is a 20% markup but only a 16.7% margin. See profit and loss explained for a full example.

How do I find the selling price for a target profit?

Multiply the cost by one plus the profit percentage as a decimal. For a cost of 80 and a 25% profit, the selling price is 80 × 1.25 = 100.

How do I find the cost price from the selling price and profit percentage?

Divide the selling price by one plus the profit percentage as a decimal. If you sold at 120 with a 20% profit on cost, the cost was 120 ÷ 1.2 = 100.

How do I calculate loss percentage?

Divide the loss by the cost price and multiply by 100. If the cost was 100 and the item sold for 85, the loss is 15 and the loss percentage is 15%.

Is profit worked out on cost or on selling price?

Both are used. Shops and school textbooks usually work on cost, while accountants often report margin on the selling price. Always state which one you mean, because the same sale gives two different percentages.

Does the calculator include rent, delivery or other expenses?

It compares only the figures you enter. If you want a true profit, add all costs that belong to the item, such as purchase price, shipping, packaging and fees, into the cost value before you calculate.

What is the break-even point?

Break-even is the selling price at which you make neither profit nor loss. It equals your total cost. Selling below it makes a loss and selling above it makes a profit.

How do I work out profit on several items?

Multiply the cost and the selling price by the number of items, or enter the totals directly. You can also find the profit on one item and multiply it by the quantity.

Why might my profit figures differ from my accountant's?

Differences usually come from definitions and scope: margin versus markup, which costs are included, and whether tax is counted. Compare figures only when both use the same definition and the same costs.

Unit and currency converter

Which kinds of conversion are supported?

The unit and currency converter handles length, weight, temperature and currency. Each category has its own list of units.

How do I convert kilometres to miles?

Multiply kilometres by 0.621371, because one mile is 1.609344 km. So 10 km is about 6.21 miles.

How do I convert inches to centimetres?

Multiply inches by 2.54. This is exact, since one inch is defined as 2.54 cm. Ten inches is 25.4 cm.

How do I convert kilograms to pounds?

Multiply kilograms by about 2.20462. One pound is exactly 0.45359237 kg, so 70 kg is roughly 154.3 lb.

How do I convert Celsius to Fahrenheit?

Multiply by 9, divide by 5 and add 32. So 25°C is 25 × 9 ÷ 5 + 32 = 77°F.

How do I convert Fahrenheit to Celsius?

Subtract 32, multiply by 5 and divide by 9. So 98.6°F is (98.6 − 32) × 5 ÷ 9 = 37°C.

What is Kelvin?

Kelvin is the absolute temperature scale used in science. Its steps are the same size as Celsius degrees, and K = °C + 273.15. Water freezes at 273.15 K.

How many feet are in a metre?

One metre is about 3.2808 feet. In the other direction, one foot is exactly 0.3048 metres.

How many ounces are in a pound?

There are 16 ounces in a pound. One ounce is about 28.35 grams.

Is a metric tonne the same as a ton?

No. A metric tonne is 1,000 kg and is the unit used in our converter. A US short ton is 2,000 lb, about 907 kg, and a UK long ton is 2,240 lb. Read more in common unit conversions made simple.

Where do the currency rates come from?

When it is available, your browser requests public reference exchange rates from a third-party service. If that request fails, the tool shows approximate built-in rates and says so under the converter.

Can I rely on the currency converter for payments?

No. Rates are for general guidance only. Banks and exchange services add their own margins and fees, so check the exact rate with your provider before you send or exchange money.

Which currencies can I convert?

The converter includes OMR, USD, PKR, INR, EUR, GBP, AED, SAR, BHD, QAR, KWD, JPY, CAD and AUD.

Why does my bank give a different rate from the converter?

Reference rates are close to the middle of the market. Banks and exchange shops quote separate buy and sell rates, add fees and update at different times, so the figure you receive is usually lower.

Basic calculator

How do I use the basic calculator?

Tap the number keys, choose an operation such as add, subtract, multiply or divide, enter the next number and press equals. The clear key starts a new calculation. There is a short guide on the basic calculator page.

Is the calculator free and does it need sign-up?

It is free and needs no account. Open the page and start calculating.

Does the calculator work on a phone?

Yes. The keypad is designed for touch screens and the layout adapts to small and large screens.

Do I need an internet connection to calculate?

Calculations run in your browser, so once the page has loaded, simple sums do not contact our server. You still need a connection to open the page, and the currency converter needs one to fetch rates.

How can I double-check a calculation?

Estimate the answer first by rounding the numbers, then compare it with the result. For an important sum, repeat it in a different order or with a second tool.

Can I use the calculator for percentages and discounts?

You can, but the percentage and discount calculator is built for it. It has separate modes for a percentage of a number, a discounted price and an added percentage.

About the site

What is SmartCalc Converter?

It is a free website that brings a basic calculator, a percentage and discount tool, a profit and loss calculator and a unit and currency converter into one place. Read more on the About page.

Is SmartCalc Converter free?

Yes. All tools are free to use.

Do I need to create an account?

No. There is no sign-up or login.

Are the numbers I enter stored?

No. Calculations are processed on your device and are not sent to or stored on our servers. The only outside request is for currency rates. Details are in the Privacy Policy.

Does the site use cookies?

The tools themselves do not need cookies. Google Analytics, which we use to count visits, may set cookies or use similar technology, as explained in the Privacy Policy.

Does the site work on mobile and desktop?

Yes. It is built to be fast and readable on phones, tablets and computers, in any modern browser.

How accurate are the results?

The tools use standard formulas. Results are for general guidance. For invoices, taxes, legal matters or big financial decisions, check the figures with your own records or a qualified professional.

How do I report a mistake or bug?

Use the contact page. Please tell us which tool you used, the values you entered, what you expected and what you saw, plus your device and browser if you can.

Can I suggest a new tool or article?

Yes. Send your idea through the contact page. We read every message, although we cannot always reply to each one.

Who runs the site?

SmartCalc Converter is an independent website. You can reach the owner through the contact page or at umarm562@gmail.com.

How can I contact you?

Fill in the form on the contact page, which opens your email app with the message ready, or write directly to umarm562@gmail.com.

Where can I learn the maths behind the tools?

Our articles explain the formulas in plain language, with worked examples for percentages, profit and loss, and unit conversions.

Do you give financial advice?

No. The site offers calculators and general information only. It is not financial, tax or legal advice.

Which language is the site in?

The site is currently in English. If you would like another language, let us know through the contact page.

Still have a question?

If you cannot find your answer here, read our articles, visit the About page or contact us. We read every message.