According to B. Graham a well-known calculation is based on the price-earnings ratio. If the ratio is high (like 30+), the price is expensive and if it’s low (<5) then it’s supposed to be cheap. But that is not so easy to say. We need to look what’s the real earning / outcome, growth, expectations and of course what “Mr. Market” is doing. Sometimes the pricing is not so important, e.g. when you invest based on idealistic reasons (Environment etc.).
Examples of P/E – You can sort all companies by P/E ratio: