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Chemistry, Physics and Lab Calculators

Calculators for science coursework and the lab bench — chemistry from molar mass to equilibrium, physics from kinematics to optics, biology and molecular-lab math, weather and earthquakes, and astronomy. Each one shows the formula, the substitution and the constants it used, so you can check your own working. Free, no sign-up.

Science & Lab Calculators

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Chemistry Calculators

Chemistry problems usually run in a chain: formula to molar mass, molar mass to moles, moles through a balanced equation, and the answer back out in grams, litres or molarity. The calculators follow that chain, so you can start wherever your problem does.

Quantities and solutions

Reactions and equilibrium

Physical chemistry and reference

Physics, Biology, Earth and Space

SubjectStart withThen
Motion and forcesKinematics or Projectile MotionForce, Inclined Plane, Momentum, Torque
Energy and workKinetic Energy and Potential EnergyWork and Power, Carnot Efficiency
Circuits and fieldsOhm's LawSeries and Parallel Resistors, Capacitor, Coulomb's Law
Waves and lightWave Speed or Wavelength and FrequencyDoppler Effect, Snell's Law, Thin Lens, Decibels
Genetics and sequencesPunnett Square or DNA to ProteinHardy–Weinberg, GC Content, Primer Tm, Sequence Alignment
Weather and EarthDew Point or Earthquake MagnitudeHeat Index, Wind Chill, Latitude Longitude Distance
AstronomySun Angle or Weight on Other PlanetsStellar Parallax, Hubble's Law, Light-Year Converter

Modern physics has its own calculators: Photoelectric Effect, De Broglie Wavelength, Time Dilation and E = mc².

Molecular biology and the teaching lab

Bench work is mostly arithmetic done carefully: a PCR Master Mix Calculator scales a recipe to the number of reactions, the Ligation Calculator sets insert-to-vector ratios, and the DNA Concentration Calculator turns an absorbance reading into ng/µL. For cell culture there are the Hemocytometer, Cell Seeding and Cell Doubling Time calculators, and the Serial Dilution, Centrifuge RPM to RCF and Standard Curve tools cover the rest. Ecology has the Logistic Growth, Mark and Recapture, Shannon and Simpson's diversity calculators.

Lab Arithmetic, Units and Significant Figures

Most wrong answers in science problems are unit errors, not arithmetic errors. Keep the units attached to every number and convert them explicitly — the calculators write the units into their working, so you can see where grams became kilograms or millilitres became litres.

QuantityValueSource
Atomic weightsIUPAC abridged standard atomic weightsIUPAC Commission on Isotopic Abundances and Atomic Weights
Avogadro constant, NA6.02214076 × 1023 mol−1 (exact)2019 SI definition
Gas constant, R8.314462618 J mol−1 K−1 (exact), or 0.082057 L atm mol−1 K−1NA × Boltzmann constant

Textbooks often round these — 6.02 × 1023 for the Avogadro constant, 1.01 for hydrogen. A small difference from a textbook answer usually comes from that rounding, not from a mistake.

A lab report states how close a result came and how sure you are of it. The Percent Error Calculator answers the first question: |measured − accepted| ÷ |accepted| × 100. The Uncertainty Propagation Calculator answers the second by carrying measurement uncertainty through any formula you type — the uncertainty of a density depends on the uncertainties of both the mass and the volume. Report the result to the precision your measurements support, using the Significant Figures Calculator on the Math Calculators shelf.

For graphs of your data, use the Charts & Diagrams shelf; for regression and t-tests, the Statistics Calculators. The Lab Report Template Generator lays out the report itself.

Frequently Asked Questions

How do I convert grams to moles?
Divide the mass by the molar mass of the substance. For 10.0 g of water (18.015 g/mol), that is 10.0 ÷ 18.015 ≈ 0.555 mol. The Molar Mass Calculator gets the molar mass from the formula and the Grams to Moles Converter shows the factor-label working.
What order do I use for a stoichiometry problem?
Balance the equation, convert each given quantity to moles, find the limiting reactant, use the mole ratio from the coefficients to get the moles of product, then convert to grams or litres. Percent yield compares the mass you actually collected with that theoretical maximum. The balancer, stoichiometry, limiting reactant and percent yield calculators follow exactly this sequence.
How do I calculate molarity and a dilution?
Molarity is moles of solute per litre of solution: 5.85 g of NaCl (58.44 g/mol) in 500 mL is 0.100 mol ÷ 0.500 L ≈ 0.200 M. For a dilution use M₁V₁ = M₂V₂ — to make 250 mL of 0.10 M from a 1.0 M stock, take 25 mL of stock and add water to the 250 mL mark.
What is the difference between percent error and uncertainty?
Percent error compares your result with an accepted value, so it needs a known answer to compare against. Uncertainty describes the spread of your own measurement and does not need one. A good lab report gives both: the result with its uncertainty, and the percent error against the literature value.
Why is my answer slightly different from the textbook's?
Usually rounding. Textbooks round constants and atomic weights — 6.02 × 1023 instead of 6.02214076 × 1023, 1.01 for hydrogen instead of 1.008 — and round intermediate results. The calculators carry full precision to the end, so the last digit can differ.