Molarity calculator
For those of us who are mathematically challenged, or those of us whose brains need a break after thinking about cutting edge research all day, we provide an easy to use molarity calculator to double check that your lab solutions are always made correctly.
The calculator solves for mass, volume, molarity, or molecular weight. Just enter any three of the numbers you know and leave the one that you don't know blank. Uses C = m / (MW × V) with consistent SI conversions (g, mg, L, mL, M, nM). The units can be mixed (for example mg with mL and M). Double-check critical stock solutions with a second calculation before preparing buffers or media in the lab.
We also provide a calculator that can be used for DNA oligonucleotides, converting ng/mL to µM. You can simply input the length of the DNA, select whether it is single stranded or double stranded and it will calculate the concentration based on the average molecular weight of a nucleotide. Remember that this will only be an approximation since your actual DNA may not have the same number of As, Ts, Gs and Cs. However, if you know the sequence of your DNA, enter it in the box to get an accurate calculation.
Uses: These calculators are intended to allow you to quickly and easily work out how to make up specific concentration solutions of lab reagents or DNA fragments and DNA oligo. The DNA calculator is also very handy for quickly converting DNA ng/mL into µM.
Lab safety note: The calculator does not replace MSDS, institutional SOPs, or other safety checks.
Enter three positive numbers; leave the fourth field empty. The answer appears in that field and below. MW is assumed in g/mol (numerically equal to Da per mole for practical use).
Click Calculate after filling three fields.
DNA concentration (ng/mL ↔ molarity)
Enter either ng/mL or molarity (leave the other blank), plus sequence or length. Residue masses (g/mol): dA 313.21, dT 304.20, dG 329.21, dC 289.18. With no sequence, 50% GC uses the mean (~309.0 g/mol per nt; ds ~618.0 g/mol per bp). C (M) = (ng/mL × 10−6 g/L) / MW; ng/mL = C × MW × 106.
Enter ng/mL or molarity (one blank) and calculate.