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Count k-length sequences from n symbols when each position may repeat any symbol (n^k cases)
Count k-length ordered selections from n distinct items without reuse—the nPk partial permutation
Calculate maximum heart rate with the Astrand age-based regression formula.
Calculate body mass index online
Compute the Luhn mod-10 check digit for a numeric identifier prefix
Derive maximum heart rate with the Cerretelli age-based formula.
Find your Chinese zodiac animal and five-element cycle from a Gregorian birth date
Flip a fair virtual coin for heads or tails—useful for quick decisions and tie-breakers.
Count multisets of size k from n types when the same element may appear more than once
Count unordered k-subsets from n distinct items without replacement—the binomial n choose k
Project savings growth with compound interest and compounding frequency
Estimate max heart rate using the Cooper formula: 220 minus your age in years.
Convert between bytes, KB, MB, GB, and TB using binary (1024-based) factors in your browser.
Recover plaintext from AES ciphertext when you supply the matching passphrase and mode
Decode legacy DES ciphertext for compatibility testing—56-bit DES is not secure today
Decrypt Rabbit stream-cipher output when you know the original secret key bytes
Decode RC4 ciphertext for legacy compatibility checks and capture-the-flag puzzles
Decrypt RC4-drop ciphertext that skips the first 256 keystream bytes before encoding
Decrypt Triple-DES (3DES) ciphertext when the same passphrase and settings were used to encrypt
Compute sale price and savings from an original price and percent off
Protect messages with AES symmetric encryption—the modern standard for confidential data
Encrypt with single DES for education and legacy interoperability, not production secrets
Encrypt with the Rabbit stream cipher—a fast eSTREAM portfolio algorithm for short payloads
Encrypt with RC4 stream cipher—deprecated in TLS but still found in older applications
Encrypt using RC4-drop, discarding initial keystream bytes to reduce bias attacks
Apply Triple-DES encryption by running DES three times for stronger legacy block protection
Apply a regex with flags to an input text and list every match found.
Convert CMYK percentages into RGB channel values
Enter a value in feet and instantly convert it to meters in your browser.
Convert a hex byte (e.g. FF) into its decimal value
Convert HTML entity references back to their original characters.
Convert RGB channel values into CMYK percentages (C, M, Y, K)
Convert RGB color channel values into hexadecimal color codes.
Parse Roman numerals and convert them back to Arabic integers.
Convert special characters into HTML-safe entity references for web markup.
Build numeric identifiers with a valid Luhn check digit for test cards and identifiers.
Compute a RIPEMD-160 hash digest from text for checksums and crypto use.
Calculate your health metrics, like LDL
Predict peak heart rate using the Liesen formula from age and gender inputs.
Look up the Mayan calendar day sign (nawal) associated with your date of birth
Calculate max heart rate using the Mellerowicz age regression formula.
Calculate modulo Processing runs locally in your browser.
Use our tool to calculate your estimated mortgage payments
Split a prize pool into five tiers using percentages you set for each place.
Compute the percentage increase or decrease between two values quickly.
Count permutations of multiset objects when symbols repeat within fixed-length patterns
Count ordered arrangements of n distinct items taken all at once—the factorial n! formula
Roll one or more dice with 2–1000 sides, optional count and modifier for tabletop play.
Randomize the order of pasted lines with optional trim and empty-line handling.
Estimate maximum heart rate with the Tanaka 208 minus 0.7 times age formula.
Convert temperatures between Celsius, Fahrenheit, and Kelvin with instant results.
Enter a regex pattern with flags and input text to check whether it matches.
Convert the time using different time zones
Create unique resource addresses
Switch between length, weight, and volume units and convert values with one tool.
Verify European VAT identification numbers against country format rules.
Paste an IBAN and validate it online
Check whether an Italian codice fiscale matches formal checksum and format rules.
Validate credit card and identifier numbers using the Luhn mod-10 algorithm.
Check whether a numeric string passes the ISO 7064 MOD-97 control test.
Verify UUID string format and validity for versions 1 through 5.
Useful running and walking tools
Estimate daily water intake from body weight using ml-per-kg guidelines
Find what percentage the first number represents of the second one.
Calculate the value when you take a given percentage of a number.
Map a birth date to one of twelve Western tropical zodiac sun signs (Aries through Pisces)