🔬 Free Online Science Tools
Free chemistry and physics calculators — molar mass from any formula, molarity and dilution, pH and buffers, half-life decay, ideal gas law, wind chill and heat index.
6 tools available · 100% free · No signup required
Molar Mass Calculator
Type any chemical formula to get its molar mass in g/mol plus a per-element table of atom counts, atomic weights and mass percent, using IUPAC 2021 atomic weights.
Molarity Calculator
Solve for molarity, solute mass, solution volume or molar mass, run a C₁V₁ = C₂V₂ dilution that tells you how much stock and how much solvent to use, and read molality and percent by mass.
pH Calculator
Convert between pH and hydrogen-ion concentration, solve weak-acid Ka problems with both the approximation and the exact quadratic, and mix Henderson–Hasselbalch buffers — all client-side.
Half-Life Calculator
Solve any of the four variables in radioactive decay — remaining amount, elapsed time, half-life or initial amount — with independent time units for t½ and t, isotope presets, and a decay curve.
Ideal Gas Law Calculator
Solve PV = nRT for pressure, volume, moles or temperature, with the correct gas constant automatically matched to your chosen units and shown on screen.
Wind Chill & Heat Index Calculator
Calculate the official NWS wind chill or heat index from temperature, wind speed and humidity, with an honest message whenever conditions fall outside where the formula is defined.
Science calculations go wrong in predictable ways: the wrong gas constant for the units you are using, a temperature left in Celsius where the formula needs Kelvin, or an approximation applied outside the range where it holds. These science tools are built around avoiding exactly those mistakes. You can work out the molar mass of any formula including nested groups and hydrates, convert between mass, moles, volume and molarity or plan a dilution, calculate pH from hydrogen ion concentration or from a weak acid's dissociation constant, model radioactive or pharmacological decay through half-lives, solve the ideal gas law for any variable, and find the wind chill or heat index for given conditions. Each one states the constants it uses and where they come from, shows the formula with your own numbers substituted, and tells you honestly when your inputs fall outside the range the equation was defined for instead of returning a confident wrong answer.
Chemistry: formulas, solutions, and pH
The molar mass calculator parses real chemical formulas rather than simple lists — nested parentheses as in iron sulfate, square brackets as in hexacyanoferrate complexes, hydrate dots as in copper sulfate pentahydrate, and multi-digit subscripts. It returns the total in grams per mole along with a breakdown showing each element's count, atomic mass, contribution, and percentage of the total, since mass percent composition is the second thing most people need. Case is treated strictly, because cobalt and carbon monoxide are written with the same letters in different cases and guessing between them would be unforgivable in a chemistry tool. The molarity calculator solves for concentration, mass or volume and handles dilutions, and the pH calculator gives both the common square-root approximation for weak acids and the exact quadratic solution, explaining when the approximation stops being valid — a nuance most free calculators skip entirely.
Physics: decay curves and gas behaviour
The half-life calculator works in any direction: how much remains after a period, how long until a given fraction is left, what the half-life must be given two measurements, or what you started with. It shows the decay constant and mean lifetime alongside the answer, plots the curve, and includes presets for the isotopes people actually look up — carbon-14 for radiocarbon dating, iodine-131 and technetium-99m for medicine, uranium-238 and caesium-137. The same mathematics describes drug elimination, so that application is noted too. The ideal gas law calculator solves for pressure, volume, moles or temperature, and its most important behaviour is invisible when it works: it picks the correct value of the gas constant for the units you selected and displays which one it used, converts your temperature to an absolute scale internally, and refuses temperatures at or below absolute zero with an explanation rather than returning a negative volume.
Weather formulas and their validity limits
Wind chill and heat index are both empirical regressions fitted to a specific range of conditions, and this is where most calculators quietly mislead. Wind chill is only defined at or below fifty degrees Fahrenheit with wind above three miles per hour; the heat index regression applies from eighty degrees Fahrenheit upward with humidity above forty percent, and needs published adjustments at very low and very high humidity. Outside those bands the equations return numbers that look plausible and mean nothing. This tool selects the appropriate formula for the conditions you enter, and when neither applies it says so — the air temperature is what you feel — rather than printing a figure. Alongside the result you get the risk band the weather service publishes, frostbite exposure time for cold conditions and the caution levels for heat, plus a dew point figure, so the output is actionable rather than just a number.