Quick percentage, discount and markup math, or verify a math expression
Math & Conversion Collection
Online Math & Conversion Tools
Percentages, expressions, dates, units, statistics, interest and time zones — everyday math in one place.
A math and conversion toolkit for engineers, students, operators and finance folks: percentage calculation, expression evaluation, date difference and arithmetic, temperature and unit conversion, statistics, compound interest estimation, ETA for running tasks, time zone conversion, Linux chmod permission math, plus a timer and benchmark builder for testing. All calculations run locally in your browser with no data submitted.
12Curated tools
3Workflows
3FAQ answers
Built for these intents
Convert temperature, time and units; compare time zones; compute date differences
Estimate budgets or returns: statistics, compound interest, ETA
Dev support: chmod permission math, timing and benchmark setup
Tools in this hub
Percentage Calculator
Calculate percentages, increase or decrease, ratios and change between values with multiple modes for everyday maths and financial quick checks. Five results.
Math Evaluator
Evaluate math expressions safely without eval, supporting functions, operators and parentheses for quick calculations and formula prototyping as you type.
Date Calculator
Add or subtract days, diff dates and format dates with time zone support, optionally skipping weekends and holidays for scheduling and deadlines. Skip weekends.
Temperature Converter
Convert between Celsius, Fahrenheit, Kelvin and Rankine with decimal precision, showing the formula so you can check science, cooking and weather data.
ETA Calculator
Compute estimated time of arrival from rate and remaining work with custom units for sprint planning and long-running batch task progress projections.
Chmod Calculator
Convert between octal and rwx Unix permission notation with special bits support, showing the owner, group and other bits for secure file permissions.
Chronometer / Stopwatch
Stopwatch with start, pause, lap and reset at millisecond precision for timing tasks, workouts and code execution, with records that survive tab reloads.
Benchmark Builder
Compare multiple operations-per-second measurements and rank them with statistical analysis, showing sample counts and variance rather than trusting one run.
Unit Converter
Convert length, weight, area, volume, speed and data storage units across metric and imperial systems with instant bidirectional swap for any everyday task.
Stats Calculator
Compute count, sum, mean, median, mode, min, max, range, variance and standard deviation from a list of numbers for data analysis, reports and stats homework.
Compound Interest Calculator
Calculate compound interest with regular monthly contributions, adjustable compounding frequency and final amount, total principal and effective return rate.
Timezone Converter
Convert any moment between world time zones with a live clock for UTC, Shanghai, Tokyo, London and more. Schedule across regions and time zones with confidence.
Suggested workflows
Everyday math
Verify a formula with the expression evaluator, then apply percentages and unit conversions to get the final number.
Time & scheduling
Compute date differences and time zone offsets, then estimate completion with ETA.
Budget & statistics
Understand the distribution with statistics, then model long-term growth with compound interest.
Why a math hub helps
Make result cross-checking a habit
Percentages, time zones and units are where mistakes hide. Validate the math with the expression evaluator first, then use the specific converter, and keep the steps at hand for cross-checking.
Fewer manual mistakes
Percentages, units and time zones are exactly where manual math goes wrong; a tool gives you an auditable result.
Covers dev and ops needs
chmod permission math, test timing and benchmark setup are everyday developer tasks, conveniently grouped with general math.
Open and run, no sign-up
Everything runs in your browser, so there is no account to create and no data left on a server.
Math tools FAQ
Which operations does the expression evaluator support?
It supports the four basic operators, powers, parentheses, common math functions and constants, evaluated with standard precedence — handy for verifying formulas and batch conversions.
Does compound interest support regular contributions?
It covers principal, rate, periods and annual or monthly compounding; for cash-flow scenarios such as recurring deposits, fill in the appropriate beginning or end-of-period values.
Can the chmod calculator work in reverse?
Yes. Enter a numeric mode such as 755 to expand its rwx bits, or toggle permission checkboxes to generate the numeric form.