# Thread: comparing apples to apples

1. ## comparing apples to apples

I'm pretty sure I read in one of these forums how to compare the cost of bleach when sold in different concentrations, but I just can't find it. If that didn't make sense, here's an example:

If 1 gallon of 6% costs \$2 and 1 gallon of 12.5% costs \$3.50, which is the better buy? Can I solve it like this? I think this may have been how the other poster figured it, but I just can't remember and my math skills are not the best.

100/6=16.67 x \$2= \$33.33
100/12.5= 8 x \$3.50=\$28.00

So if I was buying a 1 gallon bottle of 100% bleach (my clothes would never be the same) the 12.5% at \$3.50 per gallon is the better deal. BTW...I have no idea what12.5% actually costs, so if my numbers are really low, I hope no one got excited that I had found it cheap somewhere

3. ## Re: comparing apples to apples

( Bottle Size ) X ( Concentration ) / 100 = ( total chlorine in bottle )
( Bottle Cost ) / ( Total Chlorine in Bottle ) = ( Cost per ounce )

128 oz Bottle of 12 % at \$ 3.00

128 X 12 /100 = 15.36 ounces chlorine
\$3.00 / 15.36 = \$ 0.1953 cost per ounce

128 oz Bottle of 6% at \$2.00

128 X 6 / 100 = 7.68 ounces chlorine
\$2.00 / 7.68 = \$0.2604 cost per ounce

The 12% is cheaper in the long run.

Thanks!

5. ## Re: comparing apples to apples

That works, though it depends on the container sizes being the same.

I divide the price by the product of the container size and the percentage to get \$/pure oz. So:
\$2/(0.06*128) = \$0.26/oz
\$3.50/(0.125*128) = \$0.219/oz
In your example that comes out to the same thing, but it is easier to manage when the containers are different sizes.

6. ## Re: comparing apples to apples

There is more than one way to skin a cat. Both methods work.

7. ## Re: comparing apples to apples

Check the dates on the 6% bleach, because it may be old and have lost some of its potency. Most grocery store bleach is now sold in smaller bottles with 8.25% concentration. Those started showing up on shelves last pool season.

8. ## Re: comparing apples to apples

Also keep in mind that 12% breaks down rather quickly...so sometimes even though 8.25% may be a few pennies more per ounce, in all reality the effective strength might wipe out that gain.

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