What’s the best way to handle tax-inclusive prices in a calculator?

I’ve been working on a small calculator project around reverse tax calculations, and one thing I noticed is that tax-inclusive pricing can be surprisingly confusing.

For example, if a final price is $220 and the tax rate is 10%, simply taking 10% of $220 and subtracting it gives the wrong pre-tax amount. The correct approach is to divide the tax-inclusive price by 1.10, which gives $200.

I’m curious how other makers handle calculations like this in their own products. Do you usually explain the formula to users, or keep the calculation behind the scenes and just show the result?

I’m building Calculate Reverse Tax around making this process easier for people who need to work backwards from a tax-inclusive price.

If anyone has suggestions for making the calculator more useful or easier to understand, I’d genuinely appreciate the feedback.