Multiplying by a percent column acts as if the percent were in fact an integer. So 100 * 50% yields 5000 in a formula column rather than the correct result of 50.
Apologies, our percent field behaves a bit differently than it does in excel, as you’ve pointed out. We treat the percent as formatting, and then just multiply the actual numbers. We’re looking into changing the behavior so that it does what you expect. In the meantime, you can divide everything by 100 as follows:
No joke. +1 for making a percentage field type compute like… wait for it… a percentage.
PS- Sorry for the snark, but having a percentage field type that just adds a % symbol to an integer is just super funky. It makes sense to just add a % when you set the FORMATTING type to “percentage”, but not when setting the field type for a column…
This does seem to be one of the most common of Airtable 'gotcha!'s.
Until it’s fixed — and, unfortunately, the longer it goes unfixed, the greater the pressure will be on Airtable not to fix it, for fear of disrupting existing bases that have implemented workarounds — one can use the following function:
Instead of
Value * Percent
use
Value * (Percent/100)
Similarly, if calculating a percentage discount (as discussed in this post) you can use
Value * (1-(Percent/100))
to calculate the amount of {Value} after the percentage discount has been applied.