Fast, accurate calculators for finance, health, math, and more — no signup required.
CalculatorsApp provides 30+ fast, free, and accurate online calculators for finance, health, math, and everyday use. No account or signup required — just open the page and start calculating. All tools work on mobile and desktop.
Financial Calculators
Our mortgage calculator uses the standard amortization formula to estimate monthly payments based on loan amount, interest rate, and term length. The compound interest calculator shows how savings and investments grow over time with daily, monthly, or annual compounding. Use the loan calculator to break down any personal, auto, or student loan into monthly repayments and total interest paid. The income tax calculator, salary calculator, and retirement calculator help you plan your finances at every stage of life.
Health Calculators
The BMI calculator uses the World Health Organization formula (weight ÷ height²) to classify body weight — supporting both metric (kg/cm) and imperial (lbs/in) inputs. The calorie calculator uses the Mifflin–St Jeor equation to estimate your daily caloric needs based on age, weight, height, and activity level. Additional tools include body fat percentage, BMR (Basal Metabolic Rate), target heart rate, water intake, and pregnancy due date.
Math & Everyday Tools
The percentage calculator instantly handles percentage of a value, percentage change, and reverse percentage. The scientific calculator supports trigonometry, logarithms, exponents, and memory functions. Everyday tools include a unit converter (length, weight, temperature, volume, speed), GPA calculator, grade calculator, date difference calculator, fuel cost calculator, discount calculator, and currency converter with automatic geo-detection.
Frequently Asked Questions
How is a mortgage payment calculated? Monthly payment M = P × [r(1+r)^n] / [(1+r)^n − 1], where P is the principal, r is monthly interest rate, and n is number of payments.
What is a normal BMI? A BMI of 18.5–24.9 is considered a healthy weight. Under 18.5 is underweight; 25–29.9 is overweight; 30 and above is obese, per WHO classification.
How does compound interest differ from simple interest? Simple interest is calculated only on the original principal. Compound interest is calculated on the principal plus all previously earned interest, producing exponentially greater returns over time.
Are the calculators free? Yes — 100% free with no account, no subscription, and no hidden costs.
How is salary calculated after tax? Take your gross annual salary, subtract your standard deduction and personal exemptions, apply the marginal tax brackets to each portion of your taxable income, then divide the net figure by 12 for a monthly take-home figure. Our salary calculator automates every step.
What is BMR and how is it used? Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest to maintain basic functions — breathing, circulation, and cell production. Multiply BMR by an activity factor (1.2 for sedentary to 1.9 for very active) to get your Total Daily Energy Expenditure (TDEE). Our calorie calculator uses the Mifflin–St Jeor equation, validated by research as the most accurate general-purpose formula.
How do I calculate compound interest manually? Use the formula A = P(1 + r/n)^(nt) where P is principal, r is annual rate as a decimal, n is compounding periods per year, and t is years. For example, $10,000 at 5% compounded monthly for 10 years gives $16,470.09. Our compound interest calculator also shows year-by-year growth charts.
How accurate is the body fat calculator? The US Navy circumference method (used by our body fat calculator) has an accuracy of ±3–4% for most adults. For women it uses neck and waist measurements; for men it also includes the hip measurement. DEXA scans are more precise but the formula is reliable for general tracking.
Complete Calculator Directory
Financial Calculators: Mortgage Calculator — computes monthly P&I payment, total interest, and full amortisation table for any home loan. Loan Calculator — works for personal, auto, and student loans; shows payment schedule and total cost of borrowing. Compound Interest Calculator — models investment growth with daily, monthly, quarterly, or annual compounding; displays a year-by-year chart. Tip Calculator — splits restaurant bills and calculates tips at any percentage across multiple diners. Salary Calculator — converts between hourly, daily, weekly, monthly, and annual pay rates and estimates net take-home after US federal tax. Income Tax Calculator — applies 2024 US federal marginal brackets plus standard deduction to estimate your tax bill and effective rate. Savings Goal Calculator — tells you exactly how much to set aside each month to hit a target amount by a deadline. Retirement Calculator — projects your retirement nest egg based on current savings, monthly contributions, expected return, and target age. Currency Converter — converts between 30+ world currencies with geo-detection to auto-select your local currency. ROI Calculator — computes return on investment, annualised return, and net profit for any investment. Inflation Calculator — adjusts historical or future dollar amounts for inflation using CPI data. Sales Tax Calculator — adds or strips sales tax at any rate; useful for US state tax calculations.
Fitness & Health Calculators: BMI Calculator — classifies body weight using the WHO scale (underweight, normal, overweight, obese) in metric or imperial. Calorie Calculator — estimates daily caloric needs (TDEE) using the Mifflin–St Jeor equation based on age, sex, weight, height, and activity level. Age Calculator — computes exact age in years, months, and days from any birthdate. Water Intake Calculator — recommends daily fluid intake based on body weight and activity. Pregnancy Due Date Calculator — estimates due date and current gestational week from last menstrual period or conception date. Target Heart Rate Calculator — computes cardio training zones (fat burn, aerobic, anaerobic) from your age and resting heart rate. Body Fat Calculator — estimates body fat percentage using the US Navy tape-measure method. BMR Calculator — calculates Basal Metabolic Rate using Mifflin–St Jeor, Harris-Benedict, and Katch-McArdle formulas.
Math Calculators: Percentage Calculator — three modes: percentage of a number, percentage change between two values, and reverse percentage (what is X% of what number gives Y?). Scientific Calculator — full-function calculator with sin, cos, tan, log, ln, exponents, square root, pi, and memory functions. Area Calculator — calculates area of circle, rectangle, triangle, trapezoid, ellipse, and parallelogram. Fraction Calculator — adds, subtracts, multiplies, and divides fractions; simplifies results to lowest terms. Square Root / Power Calculator — computes square root, cube root, nth root, and any base raised to any exponent. Average / Statistics Calculator — calculates mean, median, mode, range, variance, and standard deviation for a data set. Triangle Calculator — solves any triangle given sides, angles, or mixed inputs using the law of sines and cosines.
Other Calculators: Date Calculator — finds the number of days, weeks, months, and years between two dates; also adds or subtracts time from a date. Unit Converter — converts length, weight, temperature, volume, speed, pressure, energy, and area between metric and imperial units. GPA Calculator — computes weighted GPA from course grades and credit hours; supports letter grades and percentage grades. Grade Calculator — calculates the minimum score needed on a final exam to achieve a target grade. Time Calculator — adds and subtracts hours, minutes, and seconds; converts between time units. Fuel Cost Calculator — estimates trip fuel cost from distance, fuel efficiency, and local price per litre or gallon. Discount Calculator — computes final price after a percentage or fixed discount; also calculates the discount percentage from original and sale price. Random Number Generator — generates cryptographically random numbers in any range; supports multiple results and seed options. Password Generator — creates strong random passwords with custom length, uppercase, lowercase, numbers, and symbols. Concrete Calculator — estimates cubic metres or yards of concrete needed for slabs, columns, and footings. Subnet Calculator — computes network address, broadcast address, usable IP range, and subnet mask from CIDR notation.