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How to make a percent (%) solution

Summary: Solutions in biology are a commonly referenced with percentages:
% solution = (dry mass in grams / volume in ml) * 100

Article created: Sept 15, 2007
Article by: Jeremiah Faith

In biology, it's pretty common for solutions to be represented as percentages (e.g. "we used 2% glucose in our media"). And while I prefer molarity, percentages are certainly easier when you're actually doing experiments, because they don't require many calculations (i.e. you can calculate everything in your head).

The best way to explain percent solutions is with a few examples. To make a 1% glucose solution, grab a 100 ml bottle, add 1 gram of glucose to your bottle and bring the volume up to 100 ml. To make a 1% NaCl solution, grab a 100 ml bottle, add 1 gram of NaCl to your bottle, and bring the volume up to 100 ml. To make a 3.75% glucose solution, grab a 100 ml bottle, add 3.75 grams of glucose to your bottle, and bring the volume up to 100 ml. Easy eh?

What if you only want 50 ml of a 1% glucose solution? Grab a 50 ml tube, add 0.5 grams of glucose to your tube, and bring the volume up to 50 ml.

So the formula is just like calculating any other old percentage:
% solution = (dry mass in grams / volume in ml) * 100