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23 Free Calculators

Math & Utility Calculators

Everyday calculations made simple. Age, unit conversions, percentages, tips, and time zones. 23 free utility calculators — no sign-up required.

Exact age in years, months, and days. Includes next birthday countdown, total days lived, day of week born, and zodiac sign.

Length Converter

mm, cm, m, km ↔ inches, feet, yards, miles.

Weight Converter

kg, g ↔ pounds, ounces, stone, metric ton.

cm to Feet Converter

Convert centimeters to feet and inches instantly. Height chart from 150–200 cm with two-way conversion.

kg to lbs Converter

Convert kilograms to pounds, stones, and ounces instantly. Reference chart from 50–150 kg.

Fuel Efficiency Converter

Convert MPG to L/100km, km/L, and Imperial MPG. Covers US and metric fuel economy standards.

Temperature Converter

Celsius ↔ Fahrenheit ↔ Kelvin.

Volume Converter

Liters, ml ↔ gallons, fl oz, cups, pints, quarts.

Speed Converter

km/h ↔ mph, m/s, knots, fps.

m², hectares ↔ acres, sq ft, sq mi.

All-in-One Unit Converter

All 6 conversion types in one tabbed tool.

Time Zone Calculator

Convert times between 40+ time zones with live world clock and meeting planner.

Percentage Calculator

Three modes: find X% of Y, what percent X is of Y, and percentage change.

Tip amount, total bill, and per-person split with rounding options.

Square Footage Calculator

Room area for rectangles, triangles, circles, and L-shapes. Add multiple rooms for total square footage.

Paint Calculator

Gallons needed for walls and ceiling based on room dimensions, coats, and doors/windows.

Concrete Calculator

Cubic yards and bags for slabs, footings, columns, and steps. Supports 40lb, 60lb, and 80lb bags.

Scientific Notation Converter

Convert any number to scientific, engineering, and E notation. Includes arithmetic and SI prefix table.

Days From Today Calculator

Find the exact date 30, 60, 90, 180, or 365 days from today. Also works backward (days ago) and supports weeks, months, and years.

Business Days Calculator

Calculate the date N business days from today, or count working days between two dates. Excludes weekends and US federal holidays.

Days Until Calculator

How many days until Christmas, New Year's, Thanksgiving, Halloween, your birthday, or any custom date? Live countdown for every major holiday.

Time Unit Converter

Convert between milliseconds, seconds, minutes, hours, days, weeks, months, and years. Live results across all 9 units as you type, with payroll and project management presets.

Pressure Converter

Convert between PSI, bar, kPa, MPa, atm, mmHg, inHg, and Pa. Presets for car tires, blood pressure, altitude, and pressure cookers.

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