FREE ONLINE CALCULATORS
Smart Calculators for a Better You
Free calculators for money, health, maths, and everyday life. No sign-up. No clutter. Just the answer, with the working shown.
Looking for one in particular? Browse the full list →
Free forever · No sign-up · Works on any device
Try it: Percentage Calculator
Try it right here. Change either number and the answer updates straight away. It also handles percent increase, decrease, and change.
Example: 20% of 150 = 30. Open the full percentage calculator →
Popular Calculators
Start with the ones people use most. Every calculator is free, works on your phone, and shows the formula behind the answer.
Mortgage Calculator
Work out your monthly payment, including extra payments and payoff time.
BMI Calculator
Check your body mass index from height and weight, with the range explained.
Percentage Calculator
Work out a percentage of a number, or how much something went up or down.
Age Calculator
Find your exact age in years, months, and days from your date of birth.
Compound Interest Calculator
See how savings grow when interest earns interest, with regular deposits.
Calorie Calculator
Estimate daily calories for weight loss, maintenance, or gain from your stats.
Fuel Cost Calculator
Estimate what a trip will cost in fuel before you set off.
Browse by Category
Four hubs, one for every kind of number.
Finance
Mortgages, loans, and interest. Each tool shows the formula and a worked example, so you can check the maths.
Examples: Mortgage · Loan · Compound Interest
Health
BMI, calories, and body measurements. Quick checks, with the numbers explained, not judged.
Examples: BMI · Calorie · TDEE
Math
Percentages and everyday arithmetic — solved step by step, so you can check the working.
Examples: Percentage · Percent Change · Percent Off
Everyday
Age, tips, and trip costs — the small sums that come up in daily life, answered in seconds.
Examples: Age · Tip · Fuel Cost
How It Works
1
Enter your numbers
Type in what you know. Every field is labelled, and the units are clear.
2
See the instant result
Your answer appears right away, with the key breakdown underneath so you can see how it was worked out.
3
Read what it means
Each result comes with a plain-language explanation, so you know what the number means and what to do next.
Why CalcKits
- Instant answers. Results update as you type — no submit button, no waiting.
- No sign-up. No account, no email, no gate between you and the answer.
- Mobile-friendly. Made to work properly on a phone, not just on a desktop.
- Formulas shown. Every result shows the formula and the working, so you can check it yourself.
Common questions
Do you store the numbers I enter?
No. The calculators run in your browser, so nothing you type is saved or sent to us.
Are the results accurate?
We use the standard formulas, and we show each one with the result so you can check it. Results are still estimates — rounded, and only as good as the numbers you enter. For money or medical decisions, confirm with a qualified professional.
Are health results medical advice?
No. Health tools give estimates to help you understand a number, not a diagnosis or a treatment plan. If something worries you, talk to a clinician.
What if a result looks wrong?
Tell us through the contact form — send the calculator name, the numbers you entered, and the result you got, and we will check it.
Can I suggest a calculator?
Yes — we add tools people ask for. Send your idea through the contact form.
Find the calculator you need
Finance, health, maths, and everyday — all free.