Free Online Calculators
Practical calculators that show their working rather than just an answer, so you can check the result and understand how it was reached.
Money
Loans, interest, tax, tips and take-home pay. Each shows the arithmetic it used, so the number can be checked rather than trusted.
Compound Interest Calculator
Estimate how a starting balance and monthly contributions could grow when interest is compounded monthly. Enter the initial amount, annual rate, time horizon, and regular monthly contribution to see future balance, total money contributed, and estimated interest. The result is a mathematical projection, not a promise of investment performance. It excludes taxes, fees, inflation, changing rates, withdrawals, and irregular deposits, and it runs privately in this browser.
Loan Payment Calculator
Estimate the monthly payment and total interest for a standard fixed-rate amortizing loan. Enter the amount borrowed, annual interest rate, and term in years. The result shows the payment, interest over the full term, and total repayment, using the standard monthly amortization formula. It excludes fees, insurance, taxes, balloon payments, variable rates, and lender-specific rounding. Use it to compare scenarios, not as an offer or approval. The arithmetic remains local.
Mortgage Calculator
Estimate the principal-and-interest payment for a fixed-rate mortgage scenario. Enter the loan amount, annual rate, and term to see the monthly payment, total interest, and total repayment. This focused mortgage calculator intentionally keeps the formula understandable and does not pretend to know property tax, homeowners insurance, HOA dues, private mortgage insurance, closing costs, or changing lender rates. Use the estimate to compare terms before checking a full lender quote. Values stay in the browser.
Percentage Calculator
Use one calculator for the three percentage questions that are easy to mix up: find a percentage of an amount, find what percentage a part represents of a whole, or measure the increase or decrease between two values. The result shows the formula as well as the answer, so you can check whether the inputs have the meaning you intended. Everything runs in this browser tab without sending your numbers to a server.
Salary Calculator
Convert an annual salary into approximate monthly, weekly, and hourly equivalents. Enter gross annual pay, hours per week, and paid weeks per year. The result is a simple gross-pay conversion before income tax, benefits, retirement contributions, bonuses, overtime, unpaid leave, and local payroll rules. It is useful for comparing job offers or translating an hourly role into an annual figure, but it is not a paycheck calculator and does not estimate take-home pay. The values stay local.
Sales Tax Calculator
Add a sales-tax percentage to an item price and quantity to see subtotal, tax, and estimated final total. This calculator is intentionally jurisdiction-neutral: enter the combined rate that applies to your transaction and remember that exemptions, shipping, discounts, local surtaxes, and tax-inclusive pricing can change the real amount. It is a quick arithmetic estimate, not tax advice. Nothing you enter leaves the browser.
Tip Calculator
Calculate a restaurant tip, the final bill, and an equal per-person share in one step. Enter the amount before tip, choose a percentage, and add the number of people sharing. The calculator does not assume a local tipping custom, tax treatment, or service charge; enter the amount and percentage you actually want to use. Results stay in this browser tab, and the visible working makes it clear whether the tip is included in the total.
Health and body
Estimates, not diagnoses. Every one of these names the formula it uses and the population it was derived from.
BMI Calculator
A body mass index calculator that accepts weight and height in either metric or imperial units and returns BMI plus the WHO weight category. The tool also computes the healthy weight band for the entered height, so the number you get is paired with the range it came from. Everything runs in this browser tab — no weight, no height, and no result is uploaded anywhere.
Calorie Calculator
Estimate daily calorie needs from age, weight, height, sex used for the equation, and activity level. The calculator shows a Mifflin-St Jeor basal metabolic rate, an activity-adjusted maintenance estimate, and a modest example deficit. It is a starting point for planning, not a diagnosis or a prescription. Bodies vary, activity estimates are noisy, and medical conditions, pregnancy, medications, and eating disorders require qualified guidance. Your values remain in this browser tab.
Due Date Calculator
Estimate a pregnancy due date from the first day of the last menstrual period and an optional cycle length. The calculator starts with the conventional 280-day, 40- week estimate and adjusts for a cycle longer or shorter than 28 days. It is not a diagnosis, an ultrasound measurement, or a substitute for prenatal care. Ovulation can vary, dates can be uncertain, and a clinician may revise the estimate. The date calculation happens locally in your browser.
Dates, grades and units
Everyday conversions where the awkward part is the convention rather than the arithmetic.
Age Calculator
Enter a date of birth and a date to calculate on to see a calendar-aware age in years, months, and days. The tool also reports the total elapsed days and the number of days until the next birthday. It does not approximate an age by dividing by 365, so leap years and the different lengths of calendar months are handled explicitly. Dates stay inside your browser and are never uploaded.
GPA Calculator
Estimate a weighted GPA from up to four courses using letter grades and credit hours. The calculator maps common US-style grades to a 4.0 scale, multiplies each grade point by its credits, and divides quality points by total credits. It is a planning tool, not an official transcript calculation: schools vary in plus/minus values, repeated course rules, pass/fail treatment, honors weighting, and rounding. Check your institution's policy before submitting the number. Inputs stay in this browser.
Unit Converter
Convert everyday measurements without searching for a separate tool for each unit. Choose length, mass, volume, or temperature, enter a value, and select the source and destination units. The conversion updates immediately and keeps the original input visible beside the result, making the direction of the calculation clear. Factors are defined in the component, the arithmetic happens locally in your browser, and no measurement is sent to a server.