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Radioactivity calculator

Radioactively labeled compounds are commonly used in biological and chemical research. Use these calculators to perform the radioactivity calculations commonly used in setting up and analyzing biochemical and pharmacological experiments. Note that this page has seven independent calculators, and that the results will appear right on this page. How do these calculations work? .

NOTE: The calculations are performed by JavaScript, which is built in to of Netscape and Internet Explorer. Your browser does NOT support JavaScript -- probably because JavaScript (or VBscript) is disabled in an Options or Preferences dialog. Although you can see the calculators below, they won't work.

Isotope decay

Isotope: 125 I   32 P   33 P   35 S   3 H   Other
Half life (days):
Number of days:

Concentration of stock

% remaining isotope:
Original dilution:
Original activity:

Assumes compound was 100% labeled originally (carrier free)

Dilution of stock

Concentration of stock solution (micromolar):
Dilute to this concentration in nM:
Final dilution volume in ml:

Specific activity (cpm/fmol)

Specific radioactivity:

Counter efficiency (%):

Cpm to fmol/mg

mg protein:

Cpm to sites/cell

cell count:

Cpm to nM