Free online calculators

Finance & money

Plan loans, project compound growth, convert currencies, and split bills.

• Loan calculator (monthly payment, interest, payoff)
  Calculate monthly loan payment, total interest, and payoff timeline from principal, APR, and term.
• Mortgage repayment planner – monthly payments, lump sums
  Simulate mortgage repayments with equal payment or equal principal methods, include bonus payments, lump-sum prepayments, and compare refinance scenarios side by side.
• Compound Interest Calculator
  Estimate future value and Effective Annual Rate from APR, compounding frequency, years, and optional monthly contributions.
• Discount calculator – stacked percentage, amount
  Enter a list price and stack percentage cuts, fixed-amount deals and coupons to see final price and savings.
• Retirement Savings Calculator
  Project your retirement nest egg by combining current savings, recurring monthly contributions, investment growth, and inflation assumptions.
• Fuel Economy, Gas Cost and Trip Cost Calculator
  Estimate your real-world fuel economy, gas cost for a drive, and total trip cost including tolls and parking.
• APR to APY (EAR) Calculator
  Use this interest rate converter to switch between APR, APY/EAR, monthly, and daily rates, or run the reverse conversion to compare loans, cards, and savings.
• Biweekly loan amortization schedule (CSV export)
  Compute a biweekly amortization schedule (26 payments/year), include extra payments, and export the table to CSV.

Unit converters

Convert everyday units quickly for study, travel, and DIY projects.

• Universal Unit Converter for Length, Area, Volume & More
  Convert length, area, volume, mass, speed and temperature units instantly.
• Temperature Converter (Celsius, Fahrenheit, Kelvin)
  Convert between Celsius (°C), Fahrenheit (°F), and Kelvin (K) with precise formulas, keyboard input, and a shareable result link.
• Length Converter (m, km, cm, mm, inch, foot, yard, mile)
  Convert lengths across metric and imperial units at once with SI‑based factors, keyboard input, and a shareable result link.
• Currency converter – manual rates, base currency
  Convert currencies with manual rates or a base‑currency cross.
• Data Transfer Time Calculator (Size, Speed, Time)
  Calculate transfer time, required speed, or transferable data size with bit/byte and SI/IEC unit conversion plus efficiency.
• Air Conditioner Size Calculator
  Estimate room AC capacity from floor area or room dimensions.
• Dimensional Weight Calculator
  Calculate parcel volume, dimensional weight, and chargeable shipping weight.
• PPM to Percent Converter
  Convert ppm to percent or percent to ppm, plus ppb, ppt, and mg/kg.

Date & time

Track schedules, deadlines, and logs with dedicated date-time tools.

• Date Difference Calculator (days, business days, Y/M/D)
  Compute days between dates, count business days and working hours, and see a year‑month‑day breakdown.
• Business Days & Countdown Calculator
  Count calendar or business days between two dates, exclude custom weekend patterns and holiday lists, and jump forward or backward by N business days.
• Time Zone Converter (Instant World Clock)
  Enter a date and time to convert between time zones, with automatic daylight‑saving shifts, presets for major cities, and a shareable result link.
• Add Hours & Minutes Calculator
  Add or subtract hours and minutes in HH:MM or HH:MM:SS format.
• Age Calculator
  Calculate exact age from date of birth in years, months and days.
• Speed–Distance–Time Calculator with Pace & ETA
  Calculate speed, distance, or time from the other two. Includes unit conversions, pace output for running, and optional ETA from a start time.
• Age Difference Calculator
  Compare two birth dates and see the exact age gap in years, months, weeks, and days, who is older, and when the younger person reaches the older age.
• Birth Year Calculator
  Estimate possible birth years from age and a reference date.

Math & statistics

Solve common classroom and analytics problems without spreadsheets.

• Pi Approximation Explorer
  Compare polygon, Gregory, Nilakantha, and Monte Carlo approximations of pi with charts, errors, examples, and shareable URLs.
• Pi Algorithm Race
  Race Gregory, Nilakantha, Machin-like, and Chudnovsky pi algorithms with fixed-time and fixed-digits modes, charts, CSV export, and shareable URLs.
• Pi Digits Generator
  Generate the first n digits of pi with a Chudnovsky-based browser tool.
• Pi Digit Lab
  Search for a digit sequence, jump to a position, move block by block, and copy a selected range inside the first n digits of pi.
• 2D graphing calculator – plot and intersect functions
  Plot up to three functions, find intercepts, intersections, and extrema, then share the graph URL with step logs.
• Quadratic & Polynomial Solver with Steps
  Solve quadratic and degree-3 polynomial equations with exact and decimal roots, discriminant checks, factorization, completing the square, graph view, and step logs.
• Fraction Simplifier & Mixed Number Converter
  Reduce any fraction, convert between improper and mixed numbers, and review Euclidean GCD steps with pie and number line visuals for lessons.
• Percentage Calculator (X% of Y, increase/decrease)
  Work out X% of Y, what percent one number is of another, and the new value after a percent increase or decrease.

Education & study

Plan GPA scenarios, track coursework, and set targets for final exams.

• GPA Calculator (Weighted & Unweighted Course Average)
  Compute weighted and unweighted GPA with editable scales, Honors/AP bumps, and shareable course tables.
• GPA Calculator — cumulative & final grade needed
  Calculate term and cumulative GPA (weighted or unweighted), convert letter↔percent, estimate the minimum final exam score to reach your target, and copy a shareable URL.
• CGPA to Percentage Converter
  Convert between CGPA and percentage using example mappings (9.5×CGPA or 10×CGPA).
• Deviation Score (T-score) & Percentile Calculator
  Calculate z-score, deviation score (T-score / hensachi), and percentile.
• Grade Calculator
  Calculate a weighted course grade or the final exam score needed to reach a target.
• Multiplication Table Generator
  Generate printable multiplication tables for 1-12, 1-20, custom sizes, blank practice sheets, skip counting, and answer keys with a reproducible seed.
• Number Bonds Builder
  Build number bonds to 10, 20, 100, or any target, then print missing-part worksheets, answer keys, and fact families with part-whole diagrams.
• Number line & interval visualizer (inequality shading)
  Shade inequalities and interval unions on an interactive SVG number line.

Life & health

Track personal indicators while keeping privacy and control offline.

• BMI calculator (kg/cm) – BMI & WHO category
  Enter weight (kg) and height (cm) to get your BMI and WHO category instantly.
• BMR & TDEE Calculator
  Calculate BMR, TDEE and daily calorie needs using age, sex, height, weight and activity level.
• Ideal Weight Calculator – Devine, Hamwi & BMI Ranges
  Estimate ideal body weight with the Devine, Hamwi, Robinson and Miller formulas, set a custom BMI goal, and compare kg/lb outputs.
• Body Fat Percentage Calculator
  Estimate body fat percentage with the US Navy circumference method or BMI (Deurenberg).
• Due Date Calculator (LMP, IVF, Ultrasound)
  Estimate your pregnancy due date and current gestational age from LMP, conception, IVF transfer, or ultrasound date.
• 1RM (One-Rep Max) & Training Weight Calculator
  Estimate your 1RM from weight and reps using common formulas, then convert to training weights by %1RM or target reps.
• Aid Station Fueling Plan
  Turn fluid, sodium, drink-carb, and gel targets into station actions with refill timing and carry limits.
• Calorie & Weight-loss Planner
  Estimate your TDEE, set a calorie target to reach your goal weight by a chosen date, or see how long it may take at your current intake.

Cooking & kitchen

Convert recipe measurements, scale batches, and stay organised in the kitchen.

• Recipe Scaler (Paste ingredients, resize servings)
  Paste a recipe ingredient list and scale it instantly by servings or multiplier.
• Cups to Grams Converter for Flour, Sugar & Butter
  Convert cups to grams for flour, sugar, butter, milk, water and more.
• Cake pan and baking sheet size converter
  Convert round, square, and rectangular pan sizes to get the batter scaling factor by area or volume.
• Microwave Wattage Converter
  Microwave wattage converter for time conversion from 1000W or 1100W to 700W, 800W, 900W, or your wattage.
• Oven Temperature Converter (°C, °F, Gas Mark, Fan)
  Convert oven temperatures between Celsius, Fahrenheit, Gas Mark, and fan-assisted (convection).
• Oven to air fryer conversion calculator (temp & time)
  Convert oven recipe temperature (°C/°F/Gas Mark) and time to air fryer settings as a quick guideline.

Choose a calculator by the job you need done

Use this directory when you already know you need a calculator, but you have not chosen the category yet. Start with the job, then narrow to one category or one page.

Pick a route by task

• Daily math and classroom work: start with Math & Statistics.
• Money, tax, loans, or pricing: start with Finance calculators or the Tax topic hub.
• Date, time, and schedule questions: start with Date & Time calculators.
• Science and engineering checks: move to Science, Physics, Chemistry, or Electronics hubs.
• Broader decision routing: use Topics when the domain is clearer than the category.

Best workflow

1. Pick one category from the job list.
2. Open one calculator inside that category.
3. Return here only if the next problem belongs to another category.

FAQ

Start with these calculator hubs

• Finance calculators
  Use this for loans, payments, rates, taxes, and money workflow questions.
• Math & statistics calculators
  Open this for algebra, geometry, percentages, distributions, and classroom math.
• Science hub
  Move here for physics, chemistry, biology, electronics, and earth-science routes.
• Topics hub
  Use Topics when the domain is obvious but the exact calculator category is not.