Get original price from percentage discount

Generic formula
=price/(1-discount)
Summary
If you have a discounted price and know the discount percentage, you can calculate the original price with a simple formula that divides the discounted price by the result of 1 minus the discount percentage.
Explanation
In the example, the active cell contains this formula:
=C6/(1-D6)
In this case, Excel first calculates the result of 1 - the value in D6 (.2) to get 0.8. Next the value in C6 (56), which represents the discounted or "sale" price, is divided by 0.8 to get a final result of 70:
=56/(1-0.2) =56/0.8 =70
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