Free online calculators

Monthly payment, total interest and a full amortization schedule.

Monthly payment and total interest, both repayment methods compared.

Final balance and year-by-year growth, with monthly deposits.

Monthly payment, amount financed and total interest on a car loan.

Convert between 32 currencies, with your own rate if you have one.

Turn a salary or hourly wage into take-home pay, paycheck by paycheck.

What an amount in one year is worth in another, with official CPI-U data through 2024.

Full payment schedule — and what an extra monthly payment saves you.

Balance at retirement and the age your savings run out.

Add or remove sales tax, with US state base rates built in.

2025 federal income tax by bracket, plus a flat state rate you enter.

Profit margin, markup and the price you need for a target margin.

How long it takes to reach a savings goal — or what to save each month.

Sale price, savings and the effective discount — with stacking done right.

The true annual cost of a loan once upfront fees are counted.

Return on investment, profit and the annualized return on your money.

Price an item from a target markup, with the profit margin it implies.

Add or remove VAT/GST, with standard rates for 27 countries built in.

Months to clear a card balance, the interest it costs, and the minimum trap.

Snowball vs avalanche: payoff order, timeline and total interest.

Monthly payment, total interest and payoff date — with the extra-payment effect.

Body mass index with category and healthy weight range.

Daily calories to maintain, lose or gain weight.

Daily calories burned, plus intake ranges for fat loss, maintenance and muscle gain.

Estimated due date, how far along you are, and the dates of each milestone.

Estimate ovulation, your fertile window and your next period from your cycle dates.

Resting calories per day, with both standard equations side by side.

Protein, fat and carb grams per day for your calorie target.

Find pace, finish time or distance from the other two, with splits for the classic races.

Body fat percentage from tape measurements, plus fat and lean mass.

Daily protein range, meal split and matching food portions.

Four clinical formulas for ideal weight, side by side.

Calories burned for any activity, from standard MET values, with a food comparison.

Estimate blood alcohol content and time back to zero.

Estimate your 1RM and see the load for every rep count.

Random numbers from any range — repeats, sorting and sorting included.

Three percentage modes: percent of, percent change, and what percent.

Add, subtract, multiply or divide fractions and see the answer in lowest terms.

Standard deviation, variance and mean, with the step-by-step table.

Margin of error and confidence interval from a mean, spread and sample size.

P-values from a z-score, or the critical z for any significance level.

Turn a raw value into a z-score, percentile and normal-curve areas, or back again.

Real and complex roots, the discriminant, the vertex and the factored form.

Volume and surface area for boxes, cylinders, cones, spheres and pyramids.

Slope, angle, distance and line equation from two points.

Convert to and from scientific notation, and multiply, divide, add or subtract in it.

Any power, including negative and fractional exponents, with the same-base laws.

Log base b of a number, with ln, log2 and log10 beside it.

The square root or n-th root of a number, simplified and checked back.

Area of rectangles, circles, triangles, trapezoids and parallelograms.

Any one of radius, diameter, circumference or area fills in the other three.

Simplify ratios, complete proportions and split totals in a given ratio.

Mean, median, mode and range from a pasted list of numbers.

Type a full expression and get the answer as you type.

All sides, angles, area and perimeter from SSS, SAS, ASA or SSA measurements.

Difference between two times, or add and subtract time amounts.

Days, weeks and months between two dates — business days included.

Exact age in years, months and days — plus next birthday countdown.

Hours worked between two times — h:mm and decimal, overtime split included.

Convert a time between two zones, with the hour difference and a city board.

Days, weeks, hours and weekdays between today and the date you pick.

Daily hours, weekly total and the over-40 overtime split for a full time card.

Convert length between metric and imperial units, with exact factors.

Convert square feet, acres, hectares and square miles exactly.

Convert decimal, hex, binary and octal numbers, with the steps.

Convert Celsius, Fahrenheit and kelvin, with the formula shown.

Convert liters, gallons, cups and fluid ounces with exact factors.

Convert kilograms, pounds, ounces and stones with the exact factors.

Convert psi, bar, kPa, joules, calories, kWh, horsepower and BTU.

Convert km/h, mph, m/s, ft/s and knots with the exact factors.

Tip, total and per-person split for any bill — rounding included.

Roll any dice pool and see the exact odds of every total.

Strong random passwords, rated by their entropy in bits.

Trip fuel cost, cost per mile, and real mpg from your own fill-ups.

Handicap index from your scores, course ratings and slopes.

A playful name-match score — for entertainment only.

Convert shoe sizes between US, UK, EU and CM, with half-size rows.

Best bedtime or wake-up time from 90-minute sleep cycles.

Diameter, sidewall, revs per mile and speedometer error for any tire size.

Cubic yards, bags and weight for slabs, footings and columns.

Total floor area and perimeter across multiple rooms.

Volume, tons and coverage for gravel, stone and road base.

Wall area, gallons and cans of paint, plus primer.

Tiles, boxes and thinset for any floor or wall area.

Roof area, squares and bundles of shingles for any roof pitch.

Decking boards, joists and screws for a wood deck platform.

Cooling BTU, AC tonnage and heater kW for a room.

Cubic yards, bags and tons of mulch for every bed you enter.

Riser height, steps, run and stringer length from the total rise.

Weighted GPA from letter grades and credits, with target planning.

The score you need on the final exam to finish with the grade you want.

Weighted course grade from your scores, with letter grade and breakdown.

Letter grades and GPA points in both directions, on the 4.0 or 4.3 scale.

Score percentage, letter grade and class-curve position from your test result.

What one appliance costs to run per day, month and year.

Voltage, current, resistance and power from any two of them.

Volts lost along a run, the percentage drop, and whether it passes the 3% check.

Torque, force, volts or kW into horsepower, with quarter-mile estimates for scale.

Lumens to watts by bulb type, watts back to lumens, with room targets and lamp counts.

Real, apparent and reactive power plus the current, single or three phase.

Read a resistor from its colors, or find the colors for a resistance value.

Network, broadcast, host range and netmask from an IPv4 address and prefix.

AWG to diameter, mm², resistance and ampacity — or the nearest AWG for a metric cable.