Date, Math and Hash Calculators
These calculators answer questions about numbers and dates: what date is 90 days from now, how many working days sit between two dates, what a scientific or bitwise expression evaluates to, and how eight hash functions compare on the same input. Project planners, developers, students and anyone checking a contract deadline use them.
4 free tools · no sign-up · no ads
All Calculation Tools (4)
Which tool do I need?
Work out the date 90 days from today
Set the base date, choose Add, enter 90 days and read the result in local and UTC formats.
Count working days between two dates
Enter both dates to get total days plus a split into business days and weekend days.
Calculate with trig functions or in hexadecimal
Use scientific mode for functions and constants, or programmer mode for HEX, BIN and bitwise operations.
Compare MD5 and SHA-256 output for the same text
Enter the input once to see eight digests with their lengths, notes on safe use and timings.
About Calculation Tools
The two date tools are mirror images. Date Arithmetic starts from a date and an amount and gives you a new date in local, ISO 8601 and RFC 7231 formats. The Date Difference Calculator starts from two dates and gives the gap in several units, including business and weekend days. The Advanced Calculator has basic, scientific and programmer modes and evaluates expressions with the mathjs library and rounds results to 14 significant digits, so 0.1 + 0.2 shows 0.3. Hash Comparison is the specialist: it runs MD5, SHA-1, the SHA-2 family, Keccak-512 and RIPEMD-160 on one input and shows each digest with a timing. For unit and timestamp conversion, see Converters; for clocks and cron schedules, see Time Utilities.
Business days exclude weekends only, so subtract public holidays yourself. Month arithmetic is not reversible: adding a month to 31 January and subtracting it again does not return 31 January. Date tools use your browser's time zone. Hash timings come from your browser and vary run to run; they show relative cost, not server throughput, and none of these hashes should be used alone to store passwords.
Guides
- Date Math for Developers: Month Ends, DST Days and Unix TimeCounting days between dates, adding months without landing in March, surviving 23-hour days and reading Unix timestamps in the right unit.
- Why 0.1 + 0.2 Is Not 0.3: Calculator Precision, Precedence and RadiansFloating point rounding, operator precedence, radians versus degrees and bitwise maths: the four places calculators and code most often disagree, with worked examples.
- Comparing Hash Algorithms: Security Margins, Speed and the Keccak TrapHow digest size maps to real security, why MD5 and SHA-1 fell, when SHA-512 beats SHA-256, and why a library called SHA3 may not give SHA-3 output.
Frequently asked questions
Why do some calculators say 0.1 + 0.2 is 0.30000000000000004?
Because they show raw binary floating point, which cannot store 0.1 exactly. Calculators that round the displayed result, as the Advanced Calculator here does to 14 significant digits, show 0.3.
Do online date calculators count public holidays?
Not here. Business day counts exclude Saturdays and Sundays only, because holidays differ by country and region. Subtract your local holidays from the result.
Why does adding one month to a date sometimes land on an odd day?
Months have different lengths, so the day of the month may not exist in the target month and gets moved. Adding then subtracting a month can therefore end on a different date than you started.
Is the fastest hash function the best one to use?
No. Speed suits checksums and caching, but for passwords you want deliberately slow, salted functions such as bcrypt, scrypt or Argon2. MD5 and SHA-1 are also broken for collision resistance.