Solution Preparation Calculator - C1V1 dilution, molarity & mass, buffer pH (Henderson-Hasselbalch)

Mode

Dilution (C1V1 = C2V2)

Stock conc. C1

Volume of stock V1

Working conc. C2

Final volume V2

Concentration unit (shared by C1/C2)

Volume unit (shared by V1/V2)

Leave exactly one of the four blank and it is solved. C1/C2 must share a concentration unit and V1/V2 a volume unit - they need not be molar (% or mg/mL work too).

e.g. from 10 mM stock make 500 mL of 0.5 mM

Result

Common buffers: pKa and molar mass

pKa values are the 25 °C literature convention (handbooks differ slightly); MW matches the usual hydrated form. Tris has d(pKa)/dT ≈ -0.028/°C, i.e. pKa ≈ 8.5 at 4 °C - convert when preparing cold buffers.

What this tool is

SolutionCalc merges the three lab calculations people otherwise do in their heads into one page: (1) C1V1=C2V2 dilutions with any single term solved; (2) molar preparation interconverting molar mass, concentration, mass and volume via m=C·V·MW; (3) buffer pH recipes from the Henderson-Hasselbalch equation, in two bench styles - mixing two equimolar stocks in the 10^(pH-pKa) ratio, or weighing the solid and titrating with HCl/NaOH to target pH. Data for 18 common buffer systems (acetate, citrate, MES, PIPES, MOPS, phosphate, HEPES, Tris, glycine, carbonate...) ship with the page.

Everything is computed in your own browser: the tables ship with the page, there is no backend and no recipe is uploaded. Your inputs are kept in local storage, the result copies into your notebook with one click, and units convert at the input side (M/mM/µM, g/mg/µg, L/mL/µL) with readable magnitudes chosen for the output.

Features

Solve any dilution blankLeave out C1, V1, C2 or V2 and it is computed; the two concentrations just need a shared unit, molar not required.

Moles ↔ mass ↔ volumeMW, C, m and V interconvert with unit selects and automatic output magnitudes (g/mg/µg, mL/µL).

Two buffer recipe stylesEquimolar stock mixing returns pipetting volumes; weigh-and-titrate returns mass plus titrant volume, picking HCl or NaOH from the form you weigh.

18-buffer data tableAcetic, citric (three pKa), MES, PIPES, MOPS, phosphate, HEPES, Tris, Bicine, TAPS, glycine, bicarbonate - hydrate-aware MWs and a buffer-capacity warning outside pKa ±1.5.

Live and copyableEvery keystroke recomputes; copy the result block as plain text.

Dark mode, three languagesLight/dark theme and Simplified / Traditional Chinese / English interfaces; pure front-end, recipes stay local.

How to use it

Pick a mode up top: dilution, molarity & mass, or buffer pH.

For dilution and molarity fill the knowns and leave exactly one field blank - the answer appears below instantly.

For buffers pick the system (pKa auto-fills), enter target pH, final concentration and volume; add the stock concentration (two-stocks) or titrant concentration and optional purity (weigh-and-titrate).

Copy the result; a capacity warning shows when the target pH is more than ±1.5 from the pKa.

FAQ

What is Henderson-Hasselbalch and how is it used here?

pH = pKa + log([A-]/[HA]), i.e. the base/acid mole ratio r = 10^(pH-pKa). The two-stock mode splits the stock volumes by that ratio; the titration mode takes the total moles n = C·V and asks how much strong acid/base converts the weighed form into the target ratio - which becomes the titrant volume. At pH = pKa the two forms are 1:1; buffer capacity falls off as you move away.

Why dissolve in only 80% of the water first?

Adjusting pH after making up to volume changes the volume and the concentration. Dissolving in ~80%, titrating, then topping to the mark keeps the final molarity honest - and the titrant itself adds volume. Calibrate and read the pH meter at roughly the temperature you will use.

Tris at 4 °C - which pH do I target?

Tris carries d(pKa)/dT ≈ -0.028/°C: 8.07 at 25 °C becomes about 8.5 at 4 °C, so the same solution reads ~0.4 higher when cold. Decide the target at the temperature of use; this tool's table is the 25 °C convention.

How do hydrates and purity fold in?

Cleanest: use the molar mass printed on your bottle - Na2HPO4·12H2O is 358.14, anhydrous 141.96. For assays below 100% (damp reagent, 99.5%) the weigh-and-titrate panel has a purity box: weigh = nominal ÷ fraction.

Are my recipes uploaded?

No. Fully static page, no backend; concentrations and masses are computed locally and only your inputs are kept in this browser's localStorage. Unpublished formulations are safe.

SolutionCalc Solution Prep

Mode

Dilution (C1V1 = C2V2)

Molar preparation (m = C·V·MW)

Buffer pH preparation

Result

What this tool is

Features

How to use it

FAQ

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