Assay Open calculator

BENCH MATH, EXPLAINED.

Lab calculations
that show
their work.

Molarity, dilutions, protein properties and PCR recipes. The everyday numbers, with the methods and assumptions where you can see them.

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Free core calculators · Optional Pro, one-time purchase
No account. No ads. Installed calculators work offline.

TRY A CALCULATIONFREE

From stock to working solution.

Both concentrations in mM; final volume in µL. Change the numbers to see the result.

Use a decimal point; no thousands separators.

STOCK TO ADD

10 µL

+ 990 µL diluent

V₁ = C₂ × V₂ / C₁ = 0.1 × 1000 / 10

A starting point for your protocol. Verify units, reagent identity and instrument limits before use.

MolarityDilutionProtein MW & εOligo TmPCR recipesRCF ↔ RPM

LESS RE-TYPING. MORE BENCH WORK.

Your next reading.
Your familiar recipe.

Pro is built for the calculations you come back to. Keep your named constructs and mixes on your device.

PRO · PROTEIN WORK

Sequence to concentration,
with your construct.

  1. Build it. Add tags and a cleavage site to the core sequence. Inspect the expressed or cleaved product.
  2. Save it. Keep its name and construct configuration; reload it when you need it.
  3. Use it. Enter a 1 cm-normalized A₂₈₀ reading for mg/mL and µM. Reuse its MW in molarity.
Saved structure, not another sequence to paste.
PRO · PCR / qPCR

The same mix.
A different number of wells.

  1. Name your recipe. Save components and per-reaction volumes.
  2. Scale the setup. Set reaction count and overage. Keep template separate.
  3. Take it to the bench. Copy the valid recipe with its warnings. Reload the mix for the next run.
Drafts stay put when you switch tools.

START WITH THE CALCULATION YOU NEED

Free for the basics.
Pro for the repeat work.

ASSAY

Free

Check a result before deciding to upgrade.

  • Molarity, percent conversion, dilution and resuspension
  • Protein properties, oligo Tm and DNA/RNA concentration
  • Ligation ratios, sequence tools and buffer pH
  • Agarose gels and RCF ↔ RPM
  • One saved construct and one saved rotor
Open the free calculators →

ASSAY PRO

One purchase.
No subscription.

Your local library and recurring workflows.

  • Tagged constructs with saved builder configuration
  • A₂₈₀ → concentration using the construct’s ε
  • PCR/qPCR scaling and named saved mix recipes
  • Serial-dilution planning
  • Single-powder preparation with purity correction
  • Unlimited saved constructs, rotors and mix recipes
Get Assay on the App Store ↗

US price: $9.99. Your local price is shown in the app before purchase. Pro is purchased in the iOS app.

The web version previews the free tools. Pro ownership restores with your Apple ID; saved lab data remains local to each device.

KNOW WHAT THE NUMBER MEANS

Methods you can inspect.
Limits stated plainly.

Assay uses deterministic equations. It does not use AI to generate scientific results. Models describe particular conditions; they do not validate your experiment.

Concentrations, dilutions and recipes

Molarity follows m = C × V × MW; dilution follows C₁V₁ = C₂V₂. Recipes scale the entered amounts and make their unit assumptions visible. Impossible dilution and recipe inputs block the usable result. Small-volume warnings use a 0.5 µL reference threshold; your pipette and protocol may require a higher minimum.

Protein MW, extinction and pI

MW sums average residue masses plus water. ε₂₈₀ uses 5,500 per Trp, 1,490 per Tyr and 125 per cystine for the oxidized estimate. A₂₈₀ concentration assumes a 1 cm-normalized absorbance. Theoretical pI uses a residue-dependent termini model. Modifications, actual disulfide bonding and experimental conditions can change the result.

References: ExPASy ProtParam methods; Pace et al. (1995). These are theoretical estimates, not a claim of universal experimental accuracy.

Oligo Tm and sequence tools

Unmodified DNA oligo Tm uses the complete SantaLucia (1998) nearest-neighbor parameter set with monovalent-salt and strand-concentration assumptions. It does not include Mg²⁺/dNTP corrections, secondary structures or modified bases. Translation uses the standard genetic code. Multiple FASTA records must be handled individually.

Reference: SantaLucia, PNAS (1998). Tm is a model estimate, not a prescribed PCR annealing temperature.

How we check the calculations

Automated tests cover unit conversions, published model fixtures, ambiguous sequences, domain boundaries and invalid recipes. The app shows methods and assumptions alongside results. A passing test suite is not validation of a physical laboratory experiment.

If a result disagrees with your reference, send a reproducible, non-confidential example so we can investigate.

YOUR SCIENCE STAYS LOCAL

No account.
No ads.

Entered sequences, calculation values and saved lab data are processed on your device. Installed calculators work without an internet connection.

Optional public UniProt lookups, opt-in usage analytics and App Store purchases use the internet. Analytics never includes your scientific inputs or saved names.

Read the privacy policy →

Ready for the next calculation?

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Free to download. Optional one-time Pro.