I search regularly FTSE100 for inexpensive stocks and even when the index is at all-time highs, I still find deals.

The quickest way I know to tell if a stock is a good value is to check its price-to-earnings ratio. Other measures include price-to-book and discounted cash flow, but this is my first port of call.

Using the P/E ratio, three companies stand out, but with a caveat. Cheap doesn’t automatically mean it’s a good time to buy. Sometimes there is a very good reason why a stock is in the bargain bin.

EasyJet shares grounded

I chose a budget carrier easyJet (LSE: EZJ) for a while. It looks shoddy with a P/E ratio of 7.6, but it’s struggling to achieve launch velocity.

easyJet shares have fallen 5% in the last year, at a time when they have been trading flat on the FTSE 100 International consolidated airline group increased by 103%. easyJet operates in the European market, while IAG benefits from transatlantic traffic.

easyJet’s July 17 results showed a pre-tax profit of £286m for the three months to June 30, up £50m year-on-year due to robust demand and the Easter period.

While this was good news, shares have fallen recently as French air travel strikes threaten to wipe out £25m from their profits, with travelers booking tickets later amid global economic problems. Despite these risks, I believe this is an option worth considering due to its long-term comeback potential. But only in the long term, because given today’s economic turmoil, I think it may face further adversity.

JD Sports shares are rising

Trainer and sports goods seller JD sports fashion (LSE: JD) also looks like a great value with a P/E ratio of 7.9, but its shares have lost a lot of value. They are down 25% over the past year, despite a 60% augment over the past six months.

I bought shares 18 months ago with the hope of participating in their recovery, and now I am back in the black and counting on further growth. I may have to be patient though.

Consumers remain in control, including in the US, where JD Sports now generates almost 40% of its sales. Tariffs remain an issue. Still, I think today’s low valuation provides a potential entry point for investors willing to weigh the ups and downs. That’s exactly what I plan to do.

WPP is the FTSE 100 falling knife

Media and advertising group WPP (LSE: WPP) is the cheapest of the three with a P/E ratio of 7.3. However, I recommend being especially careful when tempted.

WPP’s share price is down 53% over the past year and 80% from its early 2017 peak. The problems came to a head with the departure of the group’s charismatic but controversial leader, Martin Sorrell, in April 2018, and since then the news has been bad.

The company has been affected by the economic slowdown and now also by the potential threat posed by artificial intelligence, which may allow clients to cheaply produce advertising campaigns themselves.

WPP is currently the fastest falling knife on the FTSE 100. The idea of ​​getting caught today seems seriously hazardous to me. I love a bargain, but struggling companies take a long time to turn around. In my opinion, it is too early to consider purchasing. Of the three, I like JD Sports the most.