Lab Calculation Guides
Every guide walks through one calculation by hand — the formula, the units, a worked example with real numbers, and the sources behind it — then links straight to the matching calculator so you can run your own values. All 36 guides are free, run locally in your browser, and nothing you enter is uploaded or stored.
LaboratoryCalculators for Laboratory
Solutions, dilutions and concentration math
- How to Calculate a DilutionCalculate any dilution with C1V1 = C2V2: find the stock volume, diluent volume, dilution factor or final concentration, with ratio and percentage tables.
- How to Calculate Molar MassCalculate molar mass from any formula: sum atomic masses, handle hydrates, and convert grams to moles. Worked examples for H2O, NaCl and glucose.
- How to Calculate MolarityCalculate molarity in three steps: convert mass to moles, volume to litres, then divide. Worked examples for NaCl, glucose and a 10 mM reagent.
- How to Make a Serial DilutionPlan a serial dilution: choose the factor and tubes, see tube-by-tube concentrations, transfer and diluent volumes, and avoid common pipetting errors.
- How to Make a Stock SolutionMake a stock solution by weighing a solid or diluting a liquid: mass = MW × M × V, the 80% rule, hydrate and purity corrections, and per-compound recipes.
- How to Prepare a Working SolutionTurn a stock into a working solution with C1V1 = C2V2: dilution-factor table, step-by-step workflow, per-compound examples and a ratio crosswalk.
- Molarity vs MolalityMolarity is moles per litre of solution, molality per kg of solvent. See the formulas, the temperature difference, why molality exists, and M vs m vs N.
- Percent Solutions: w/v, v/v and w/wThe four percent-solution types compared side by side with formulas, units and worked examples, plus how to convert w/v to w/w using density.
- PPM to mg/LConvert ppm to mg/L and back, why 1 ppm ≈ 1 mg/L only in dilute water, and the full crosswalk to µg/mL, ppb, % and mg/m³ in air, with examples.
- The C1V1 = C2V2 EquationC1V1 = C2V2 explained: what each term means, all four rearrangements, the unit-matching rule, and how 10x stock maps to 1:10 and 1:100 dilutions.
- What Is Molarity?Molarity is moles of solute per litre of solution. Learn the formula, M vs mM, worked examples and why temperature changes the answer.
DNA & RNACalculators for DNA & RNA
Sequence, molecular weight and quantitation
- How to Calculate DNA Concentration from A260Convert an A260 reading to DNA concentration: the 50/33/40 factors, where they come from, dilution factor and path length, and ug/mL to nM by hand.
- How to Calculate DNA Molecular WeightCalculate the molecular weight of a DNA oligo by hand: free-acid residue masses, the terminal correction, 5'-OH vs 5'-phosphate, and ug-to-nmol.
- How to Calculate GC ContentCalculate the GC content of a DNA or RNA sequence: GC% = (G + C) / length × 100, with worked examples, IUPAC degenerate-base rules and why GC% matters.
PCR & qPCRCalculators for PCR & qPCR
Primers, master mix and amplification efficiency
- How to Calculate Delta Delta Ct (2^-ΔΔCt)Work the Livak 2^-ΔΔCt method by hand: normalise to a reference gene, subtract the control, convert to fold change, and check efficiency and error first.
- How to Calculate Primer TmCalculate primer melting temperature (Tm) two ways: the quick Wallace rule and the SantaLucia 1998 nearest-neighbour method, with a worked example.
- How to Calculate qPCR EfficiencyCalculate qPCR amplification efficiency from a standard curve by hand: regress Cq on log10 concentration, why slope -3.32 is 100%, and the 90-110% window.
- How to Choose a PCR Annealing TemperaturePick a PCR annealing temperature from primer Tm: the empirical Tm−5 start, the Rychlik Ta-optimum formula, gradient windows and mismatched primer pairs.
- How to Make a PCR Master MixMake a PCR master mix for any recipe: solve each component with C1V1=C2V2, scale by reactions plus overage, and balance the water.
Cell CultureCalculators for Cell Culture
Counting, viability, seeding density, doubling time and CFU
- How to Calculate Cell Seeding DensityWork out seeding density by hand: target density to cells per well, the growth-area conversion, and C1V1 = C2V2 to get the volume of stock to pipette.
- How to Calculate Cell Viability with Trypan BlueCalculate cell viability by hand from trypan blue counts: viability % = live/total × 100, viable cell density, the ~90% threshold and the read window.
- How to Calculate CFU/mL from Plate CountsCalculate CFU/mL by hand from colony counts: the dilution factor, plated volume, the 25–250 countable range, plate selection and why a CFU is not one cell.
- How to Calculate Population Doubling TimeDerive doubling time by hand from two cell counts: Td = t·ln2/ln(Nt/N0), the log₂ form, specific growth rate, PDL vs passage number and the log-phase rule.
- How to Count Cells with a HemocytometerTurn hemocytometer counts into cells/mL by hand: the 1e-4 mL chamber volume, why you multiply by 10⁴, the border-cell rule and dilution factor.
ProteinCalculators for Protein
Molecular weight, isoelectric point and A280 concentration
- How to Calculate Protein Isoelectric Point (pI)How to calculate a protein's isoelectric point (pI) from sequence: ionizable groups, pKa values, the net-charge sum and why you must iterate.
- How to Calculate Protein Molecular WeightSum the residue masses and add one water to get a protein's molecular weight in Da and kDa — worked example, average vs monoisotopic, and sources.
- How to Determine Protein Concentration from A280Determine protein concentration from A280: derive ε280 from Trp/Tyr/Cys, apply Beer–Lambert, and convert absorbance to mg/mL and µM with worked examples.
Molecular CloningCalculators for Molecular Cloning
Plasmid molecular weight, ligation ratio and transformation efficiency
- How to Calculate a Ligation Ratio (Insert:Vector)Calculate the insert:vector molar ratio for a ligation: convert fragment sizes and vector mass into the ng of insert to add, or reverse from masses used.
- How to Calculate Plasmid Molecular WeightCalculate plasmid molecular weight from length in bp on the 660 g/mol·bp convention, then convert to pmol/µg, molarity, molecules and copy number.
- How to Calculate Transformation Efficiency (CFU/µg)Calculate transformation efficiency in CFU/µg: apply the plated-volume dilution factor, convert DNA mass to µg, and read it against the expected range.
BiochemistryCalculators for Biochemistry
Absorbance and concentration, enzyme kinetics and buffer prep
- How to Calculate Michaelis–Menten KineticsWork the Michaelis-Menten equation by hand: solve v, Vmax, Km or [S], get kcat and efficiency, and read an inhibition pattern from apparent constants.
- How to Make a Buffer SolutionCalculate a buffer recipe the way the bench needs it: grams to weigh, mmol and mL of NaOH or HCl to add, the co-ions it leaves, capacity, and the checks.
- How to Use the Beer–Lambert LawGet a concentration from A = ε·c·l: matching units, dilution factors, transmittance, worked examples and the range where the law stops holding.
MicrobiologyCalculators for Microbiology
Optical density, cell density and plate counts
- How to Convert OD600 to Cell DensityTurn an OD600 reading into cells/mL and g DCW/L — subtract the blank, pick a cited factor, undo the dilution, stay in the linear window and calibrate.
GeneticsCalculators for Genetics
Inheritance crosses, carrier risk, probability and allele frequencies
- How to Read a Punnett SquareRead a Punnett square properly: gametes in the margins, zygotes in the boxes, and how the genotype and phenotype ratios split apart.
- How to Use the Hardy-Weinberg EquationUse p² + 2pq + q² properly: count alleles, square them, test the gap with the right degrees of freedom, read F, and invert a disease rate safely.