Free Calculators: 20 Categories of Free Online Calculators

Last updated: 22 October 2026 · By Sardar Zain, Founder of Orixiva · Reading time: 9 minutes

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What the free calculators include

The free calculators are grouped into 20 categories. Open any category to see all of its tools.

How to use the free calculators

1. Choose a tool. Use the category filter or search box above to find the right calculator.
2. Check the units. Pick the units you are working in before typing numbers, so the formula uses the right values.
3. Enter your values. Fill in every required field. Example values show the expected format.
4. Calculate and review. Read the main result, the breakdown and any notes or charts under it.
5. Save or compare. Copy, print or download the result, or change one input to compare scenarios.

Who uses these free calculators?

• Students solving maths, science and statistics problems.
• Households planning budgets, loans and everyday costs.
• Professionals in business, IT, construction and engineering.
• Cooks, bakers and fitness enthusiasts.
• Teachers preparing examples and answer keys.

Tips for accurate results with the free calculators

• Pick the category first, then the specific calculator, using the filter above.
• Check the units on every input before you calculate.
• Use the copy, print or export options to save results.
• Bookmark the categories you use most often.
• For important money, health or engineering decisions, confirm results with a professional.

Free calculators by category: what you can work out

Each category groups free calculators for one area of life or work. Here is what you will find in each one, so you can jump straight to the right page.

Money and business

The financial calculators cover loans and EMI, compound and simple interest, savings goals, ROI, inflation and sales tax. The business calculators work out profit margin, markup, break-even point and SaaS metrics. Sellers can also use the Amazon FBA profit calculator, the dimensional weight calculator for shipping and the subscription cost calculator to cut monthly bills.

School, science and data

Students and researchers can use the scientific calculator for trigonometry, logs and powers, the statistics calculators for t-tests, regression and probability, and the chemistry calculators for molarity, dilution, pH and gas laws. The data and productivity calculators help with percentages, averages and planning.

Home, cooking and building

The construction calculators estimate concrete, paint, tiles and other materials. The cooking calculator converts cups to grams and scales recipes up or down. The everyday calculators handle tips, discounts, splitting bills and other daily sums.

Health and time

The health and fitness calculators work out BMI, body fat, calories and TDEE. The date and time calculators find exact age, days between dates, working days, shift hours, running pace and sleep times.

Cars, travel and technical work

The car calculators cover fuel cost, car loans, EV charging and tyre sizes. Pilots and boat owners can plan trips with the aviation fuel calculator. The electrical and physics calculators handle Ohm's law, power and energy, and the computer calculators work out subnets, storage and download times. For any unit change, use the unit converter.

Creators and AI users

The YouTube earnings calculator estimates income and engagement rate, the AI API cost calculator compares token prices, and the 3D printing cost calculator prices prints from filament, power and time.

6 quick examples with free calculators

These short examples show the kind of answer each group of free calculators gives. You can check every one by hand.

1. Discount: a jacket costs $80 with 20% off. The sale price is 80 × (1 − 0.20) = $64, a saving of $16.
2. BMI: a person who weighs 70 kg and is 1.75 m tall has a BMI of 70 ÷ (1.75 × 1.75) ≈ 22.9.
3. Concrete: a slab 4 m long, 3 m wide and 10 cm deep needs 4 × 3 × 0.1 = 1.2 cubic metres of concrete, before any allowance for waste.
4. Download time: a 5 GB file on a 100 Mbps connection takes about 5 × 8,000 ÷ 100 = 400 seconds, or roughly 6.7 minutes, in ideal conditions.
5. Break-even: with $5,000 of fixed costs, a $25 price and $15 variable cost per unit, you need 5,000 ÷ (25 − 15) = 500 sales to break even.
6. Days between dates: from 1 January to 31 March 2026 there are 89 days, or 90 if you count both the start and end date.

Free calculators save time on sums like these and reduce mistakes, especially when there are several steps or unit changes.

How to check a result from free calculators

A calculator is only as good as the numbers you put in. Before you rely on a result, run through these quick checks:

• Check the units. Make sure lengths, weights, currencies and time periods match what the calculator expects. A monthly rate entered as a yearly rate is one of the most common errors.
• Estimate first. Round the numbers and work out a rough answer in your head. If the result is ten times bigger or smaller, look again.
• Change one input. Increase one value slightly and see if the result moves the way you expect.
• Read the formula. Most category pages show the formula used, so you can repeat the sum yourself.
• Compare with an official source. For health figures, the CDC guide to BMI explains what the numbers mean. For money, check rates with your bank or lender.

Free calculators are planning tools. For tax, legal, medical or engineering decisions, use the result as a starting point and confirm it with a qualified professional.

Free calculators for students, businesses and households

Students use free calculators to check homework, practise formulas and work through statistics for projects. Because each page explains the steps, the calculators also help with learning, not just answers. Pair them with the student and teacher toolkit to plan study time and track grades.

Small businesses use them to set prices, check margins, plan stock and estimate shipping costs. A few minutes with the business and financial calculators before a price change can prevent an expensive mistake. When the numbers are ready, the free invoice generator turns them into a professional invoice.

Households use free calculators to compare loans, plan savings, budget for home projects, scale recipes and track fitness goals. Nothing needs an account, so the whole family can use the same pages on any device.

Whoever you are, start with the category that matches your question, try the example values, then enter your own. If a calculator you need is missing, tell us through the contact page and we will consider adding it to the free calculators collection.

Free calculators vs a phone calculator or spreadsheet

A phone calculator is fine for quick sums, and a spreadsheet is great for big tables. Free calculators built for one job sit in the middle: they know the formula, ask only for the inputs that matter and explain the answer.

Common formulas behind free calculators

Many free calculators use a small set of simple formulas. Knowing them helps you spot mistakes and understand the result.

• Percentage of a number: part = whole × percent ÷ 100. For example, 15% of 240 = 36.
• Percentage change: (new − old) ÷ old × 100. A price that rises from 50 to 60 has gone up 20%.
• Simple interest: interest = principal × rate × time. $1,000 at 5% for 3 years earns $150.
• Compound interest: amount = principal × (1 + rate)^years. $1,000 at 5% for 3 years grows to about $1,157.63.
• Average (mean): add the values and divide by how many there are. The mean of 4, 8 and 12 is 8.
• Speed, distance and time: speed = distance ÷ time. 150 km in 2 hours is 75 km/h.
• Area and volume: area of a rectangle = length × width; volume of a box = length × width × height.
• BMI: weight in kilograms ÷ height in metres squared.

When a problem has several of these steps in a row, such as loan repayments or break-even with taxes, free calculators save the most time, because each step is done in the right order with the right units.

Free calculators glossary: terms you will see

Principal

The amount of money borrowed or invested before any interest.

APR

Annual percentage rate, the yearly cost of a loan including some fees.

EMI

Equated monthly instalment, the fixed monthly payment on a loan.

Margin

Profit as a percentage of the selling price.

Markup

Profit as a percentage of the cost price.

Standard deviation

A measure of how spread out a set of numbers is.

p-value

In statistics, the probability of seeing a result at least this extreme if there were no real effect.

TDEE

Total daily energy expenditure, the calories your body uses in a day.

Molarity

Moles of a substance per litre of solution.

Dimensional weight

A shipping weight based on box size rather than actual weight.

Each of these terms appears in at least one of the free calculators above, and the category pages explain them in more detail with examples.

Popular questions people answer with free calculators

Most visitors arrive with one clear question. These are some of the most common, and the free calculators that answer them:

"How much will my loan really cost?"

Enter the amount, rate and term in the loan or EMI calculator to see the monthly payment and the total interest. Then try a shorter term or a bigger deposit to see how much you could save.

"What price should I charge?"

Start with your cost, then use the margin and markup calculators to test prices. The break-even calculator shows how many sales you need before you make a profit.

"How many days until my deadline?"

The date calculators count calendar days or working days between two dates and can skip weekends, which is ideal for projects, visas, notice periods and exams.

"How much material do I need?"

The construction calculators estimate concrete, paint and tiles from your measurements, so you buy enough without paying for a large surplus. Add about 5 to 10% for waste and cuts.

"Is my result significant?"

The statistics calculators run t-tests, show p-values and explain what they mean in plain words, which helps when you write up a project or report.

"How much will this trip cost in fuel?"

Enter the distance, your car's fuel economy and the fuel price in the car calculators to get the trip cost. For example, 300 km at 7 litres per 100 km uses 21 litres; at 1.80 per litre that is about 37.80. Split it between passengers with the everyday calculators, or compare it with an electric car using the EV charging cost tool.

Using free calculators on a phone

Calculator pages are built to work on small screens, with the form and the result close together so you do not need to scroll back and forth. You can add a calculator to your home screen from the browser menu to open it like an app.

Turn your phone sideways for wide tables, and zoom in if the text is small. If something is hard to use on your device, let us know so we can improve the free calculators for everyone.

Bookmark this page so the full list of free calculators is always one tap away, at home, at work or at school.

Privacy and accuracy

The free calculators runs entirely in your browser. Numbers you type are not sent to Orixiva or stored on a server.

Results use standard published formulas and are rounded for display. They are estimates for planning, study and everyday decisions; for legal, medical, engineering or financial decisions, confirm them with a qualified professional. For background reading, see the NIST guide to SI units.

Share your feedback

Which free calculators tool did you use, and was the result what you expected? Tell other readers in the comments, or suggest a calculator we should add next. Comments are reviewed before they appear.

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