From percentage change and mortgage amortization to BMI and heart-rate estimates, these calculators explain formulas and limits on every page. Results are for learning—not professional advice.
Useful running and walking tools
Compute exact years, months, and days between a birth date and a reference date using calendar arithmetic.
Derive an Italian fiscal code from personal data, birthplace, and gender.
Estimate daily calories from lean body mass using the Cunningham RMR formula for athletes
Find the whole-day difference between a start date and end date using UTC midnight boundaries.
Convert human age to equivalent dog years based on size and weight class.
Pick a random fun pet name from a large curated list of animal names.
Calculate your health metrics, like LDL
Apply Gregorian leap-year rules to any year from 1 to 9999 and see yes or no instantly.
Estimate daily calories with the Mifflin-St Jeor resting metabolic rate equation and activity factor
Calculate modulo Processing runs locally in your browser.
Use our tool to calculate your estimated mortgage payments
Enter distance and total time to calculate your average pace per kilometer.
Compute the percentage increase or decrease between two values quickly.
Predict your finish time over a target distance from a known pace value.
Find what percentage the first number represents of the second one.
Calculate the value when you take a given percentage of a number.
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.
Compute max heart rate via the Ball State University age regression formula.
Calculate body mass index online
Find Gregorian Easter Sunday and related movable feast dates for any year.
Calculate Julian calendar Easter Sunday and linked movable feast dates by year.
Derive maximum heart rate with the Cerretelli age-based formula.
Find your Chinese zodiac animal and five-element cycle from a Gregorian birth date
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.
Select a time and start a countdown by clicking the start button, easily and online
Find elapsed days, weeks, months, and years between two calendar dates with optional direction.
Estimate ideal body weight in kg using the Devine clinical formula from height and sex.
Calculate bingo prizes using the double approach. Easily calculate your prizes!
Convert Arabic numerals (1–3999) into standard Roman numeral notation.
Parse Roman numerals and convert them back to Arabic integers.
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.
Estimate ideal body weight in kg using the Miller formula for adjusted clinical targets.
Calculate bingo prizes in percentage. Easily calculate your prizes!
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
Estimate ideal body weight in kg using the Robinson formula—a common refinement of Devine.
Discover your national holidays with this online simulator. Fill in with your country and click on the start button
Estimate maximum heart rate with the Tanaka 208 minus 0.7 times age formula.
Convert the time using different time zones
Enter distance and average speed to calculate the estimated travel time for your trip.
Optimize your vacation days with this online simulator. Fill in with your days off and start generating now
Estimate daily water intake from body weight using ml-per-kg guidelines
Map a birth date to one of twelve Western tropical zodiac sun signs (Aries through Pisces)