Sometimes you just need a quick answer. Not a spreadsheet, not a formula manual — just a simple tool that gives you a clear result based on the numbers you already have. That's what CalcTap is built for.
All 19 calculators on this site are free, require no account, and run directly in your browser. This guide walks through each one so you know exactly what it does and when it's the right tool to reach for.
Work & Pay Calculators
Whether you work variable shifts, track hourly pay, or just want to double-check a payslip, these four tools cover the most common work and payroll calculations.
Work Hours Calculator
Enter your start time, end time, and any break deductions, and you'll get the total worked hours in a clean hours-and-minutes format. It handles overnight shifts automatically — so a shift that starts at 10 PM and ends at 6 AM gives you the correct total without any extra steps. If you need the result in decimal hours for payroll or invoicing, simply divide the minutes by 60 and add them to the hours.
Salary Per Hour Calculator
Have you ever wondered what your monthly salary actually works out to per hour? Enter your monthly pay and the hours you typically work each week, and this tool gives you a practical hourly rate. It's useful when you're comparing job offers, checking whether a pay rise is meaningful in real terms, or working out a baseline freelance rate from your current employed pay.
Overtime Calculator
When you've worked beyond your standard hours, this tool estimates your extra pay based on your hourly rate, the total hours worked, and your overtime multiplier. Most employers use 1.5× (time and a half) for additional weekday hours and 2× for weekend or holiday work — but you can enter any multiplier that applies to your situation.
Hourly to Salary Calculator
If you know your hourly rate and want to see what that looks like as an annual, monthly, weekly, or daily figure, this tool calculates all four at once. It's particularly helpful when you're comparing a contract or freelance rate against the equivalent permanent salary, or when negotiating a pay package that switches between rate types.
Time & Date Calculators
Date maths is surprisingly easy to get wrong in your head. These five tools handle everything from exact age calculations to business-day counting and timezone conversions.
Age Calculator
Enter any date of birth and this tool tells you the exact age in years, months, and days as of today. It handles leap years correctly and supports dates going back more than a century, making it useful for genealogy research and historical records as well as everyday use. It doesn't require your own date of birth — you can calculate anyone's age by entering their birth date.
Timezone Converter
Scheduling across time zones is a regular challenge for remote teams and international projects. This converter uses the full IANA time zone database — the globally accepted standard — so it applies the correct daylight saving rules automatically based on the date you enter. Pick any two cities or IANA zones, enter the date and time, and see the equivalent local time in the second zone. The result also flags when the conversion crosses midnight into the next calendar day, which is easy to miss when planning meetings.
Date Difference Calculator
This tool measures the gap between any two calendar dates and breaks the result down into years, months, weeks, and days. The order you enter the dates doesn't matter — it always returns a positive result. It's useful for contracts, project timelines, anniversary counts, notice periods, and any situation where you need to know exactly how long a span of time is.
Working Days Calculator
Unlike the Date Difference calculator, this one excludes weekends and lets you subtract public holidays as well. Enter your date range and the number of holidays that fall within it, and the tool returns the net business day count. It's practical for delivery deadlines, project planning, payroll periods, and legal notice calculations where weekends and holidays don't count as working days.
Time Duration Calculator
Enter a start date and time and an end date and time, and this tool gives you the elapsed duration broken down into days, hours, minutes, and seconds. It's handy for billing by the hour, tracking how long an event ran, or calculating the duration of any past or future period where you need more precision than a date-only tool provides.
Finance & Planning Calculators
Money calculations are where a small error can lead to a big difference in practice. These nine tools help you get a clearer picture before making financial decisions — from everyday percentage checks to long-term retirement projections.
Percentage Calculator
This tool covers three common scenarios in one place: finding a percentage of a number (e.g. what is 15% of £240?), finding what percentage one number is of another (e.g. 48 out of 60 is what percent?), and calculating the percentage change between two values (e.g. a price went from £80 to £95 — what's the increase?). Useful for discounts, exam scores, profit margins, tips, commissions, and sales analysis.
Loan Calculator
Enter a loan amount, annual interest rate, and repayment term in years, and this tool shows you the monthly repayment, the total amount paid over the full term, and the total interest charged. It assumes a fixed interest rate throughout, so it's best suited to personal loans, car loans, and any other fixed-rate borrowing. Variable-rate loans can change over time, so treat the result as an estimate if your rate isn't locked in.
EMI Calculator
EMI (Equated Monthly Instalment) is the standard term for a fixed monthly loan repayment in India and many other markets. The maths is identical to the Loan Calculator — the main difference is that tenure is entered in months rather than years, which matches how most Indian banks and lenders present their loan terms. Use this when you're evaluating home loans, car loans, or personal loans from Indian financial institutions.
GST Calculator
Need to add GST to a base price, or reverse it out of an already-inclusive total? Select whether you want to add or remove tax, enter the amount, and pick your GST slab — 5%, 12%, 18%, 28%, or a custom rate. The tool instantly shows the tax amount and the gross or net figure. It's a fast way to check invoice totals and work out base prices on purchases, but it's not a substitute for proper accounting review.
Mortgage Calculator
Planning to buy a home? Enter the property price, your down payment, the expected interest rate, and the loan term, and this tool calculates your estimated monthly repayment. It also shows the total interest you'd pay over the full mortgage term — a figure that's often much larger than people expect and a useful reality check before committing to a particular loan amount or term length.
Retirement Calculator
Enter your current retirement savings, your planned monthly contribution, an expected annual return rate, and the number of years until you retire. The tool projects your future balance using compound growth. Even modest regular contributions can grow significantly over a long period, and this calculator helps you see exactly how your timeline and contribution rate affect the final figure.
Investment Calculator
Whether you're investing a lump sum, adding monthly contributions, or both, this tool shows how compound growth builds your portfolio over time. Adjust the annual return rate to compare optimistic and conservative scenarios. It's a good way to understand the long-term impact of starting earlier, contributing more, or choosing a higher-return investment strategy.
Credit Card Calculator
If you're carrying a credit card balance, this tool shows you how long it will take to clear the debt at your current monthly payment, and how much total interest you'll pay in the process. You can also try different monthly payment amounts to see how paying even a little extra each month shortens the timeline and reduces the interest cost significantly. It's often a useful motivator for paying more than the minimum.
Savings Calculator
Set a savings goal, enter your starting balance, monthly deposit amount, and an expected interest rate, and the tool projects how your savings grow over time. It's useful for short-term goals like a holiday fund, medium-term ones like a car or wedding, or longer-term goals like a house deposit. You can adjust the inputs to see how increasing your monthly contribution brings the target date closer.
Health Calculator
BMI Calculator
BMI (Body Mass Index) is a simple screening measure based on your height and weight. Enter your measurements in metric (kg and cm) or imperial (lbs, feet, and inches) and the tool gives you your BMI score along with the standard WHO category — underweight, healthy weight, overweight, or obese. BMI is a useful starting point, but it has limits: it doesn't distinguish between fat and muscle mass, so fit and muscular individuals can show a higher BMI than their health would suggest. Treat it as one data point, not a diagnosis. For any health concern, talk to a doctor.
A Few Things Worth Knowing
All CalcTap calculators are free and available without an account. The maths runs in your browser, so the numbers you enter aren't sent to a server. Each calculator page includes a short explanation of how it works and what assumptions it uses — so you know where the result is reliable and where you should verify it independently.
Results from financial, tax, payroll, and health tools are estimates. They're useful for planning and comparison, but they're not a substitute for advice from a qualified professional when the decision matters. If a result looks wrong or a tool is broken, email support@calctap.com and we'll take a look.