Biochemistry calculators and unit converters
Convert mass, moles, volume and concentration across every unit a biochemist uses — from kilograms to femtograms, from molar to attomolar. Plan dilutions and buffers, quantify protein and nucleic acids, and see the formula behind every answer.
Choose a calculator
Molarity & mass conversion
Mass ↔ moles ↔ molarity ↔ volume for any molecular weight, plus molecule counts.
- g → mol
- mg/mL ↔ mM
- weigh-out
- molecules
Dilutions
C₁V₁ = C₂V₂, fold dilutions, serial dilution series and two-solution mixing.
- stock → working
- serial
- dilution factor
Percent, ppm, molality & normality
% w/v, % w/w, % v/v, ppm/ppb and mg/dL, with density correction and equivalents.
- % ↔ M
- ppm
- mol/kg
- N
Protein concentration
A280 with molar or 0.1 % extinction coefficients, kDa ↔ molar, MW and ε from sequence.
- A280
- ε₂₈₀
- kDa → µM
- sequence
DNA & RNA
ng ↔ pmol, A260 quantification, oligo MW and Tm, plasmid copy number for qPCR.
- ng → pmol
- A260
- Tm
- copies
Buffers & pH
Henderson–Hasselbalch both ways, component weigh-out and 12 standard buffer systems.
- pH ↔ ratio
- pKa table
- recipes
Enzyme activity
Units ↔ katal, specific activity, kcat, ΔA/Δt rates and Michaelis–Menten.
- U ↔ kat
- U/mg
- kcat
- Km
Centrifugation
RCF ↔ rpm for any rotor radius, and rescaling a protocol between rotors.
- × g ↔ rpm
- rotor swap
Cell density
OD₆₀₀ → cells/mL, hemocytometer counts and seeding-volume planning.
- OD₆₀₀
- hemocytometer
- seeding
Unit reference tables
SI prefixes and conversion factors for mass, volume, amount, molarity and activity.
- SI prefixes
- tables
- any → any
Quick converter any unit → any unit
Pick a quantity, type a value, and read it in every unit at once.
| Unit | Value |
|---|
What this site does
Most bench calculations come down to four quantities — mass, amount of substance, volume and
concentration — tied together by the molecular weight of whatever you are working with. The
trouble is that the units span eighteen orders of magnitude, and half of them are written in
ways that hide their relationship: 1 µg/µL, 1 mg/mL and
1 g/L are the same number.
Every calculator here works in SI base units internally and converts on the way in and out, so you can mix units freely — enter a molecular weight in kDa, a mass in nanograms and a volume in microlitres, and read the answer in picomolar. Each result shows the formula and the intermediate values so you can check the arithmetic or reproduce it in a notebook.
The relationships behind every calculator
| Quantity | Relationship | Notes |
|---|---|---|
| Amount of substance | n = m / M | moles = mass ÷ molecular weight |
| Molarity | c = n / V | mol per litre of solution |
| Mass concentration | ρ = c × M | g/L ≡ mg/mL ≡ µg/µL |
| Molality | b = n / m_solvent | mol per kg of solvent; temperature-independent |
| Normality | N = c × z | z = equivalents per molecule |
| Dilution | C₁V₁ = C₂V₂ | solute is conserved |
| Particle number | N = n × N_A | N_A = 6.022 140 76 × 10²³ mol⁻¹ |
| Beer–Lambert | A = ε c l | basis of A280, A260 and kinetic assays |
| Buffer pH | pH = pKa + log₁₀([A⁻]/[HA]) | Henderson–Hasselbalch |
| Centrifugal force | RCF = 1.118×10⁻⁵ r N² | r in cm, N in rpm |
Accuracy and constants
Atomic and physical constants follow the 2019 SI redefinition (NA = 6.022 140 76 × 10²³ mol⁻¹ exactly). Amino-acid residue masses are monoisotopic-averaged values; nucleotide masses use the sodium-salt convention (617.96 g/mol per base pair of double-stranded DNA). Extinction coefficients at 280 nm follow Pace et al. (Protein Science 1995). Results are shown to four significant figures.
Everything runs client-side in JavaScript. No values you enter leave your machine, and the pages work with no network connection once loaded.