Forward P/E Explained: Why Tech Stocks Look Cheap

You opened your brokerage app on November 5 and watched a month of gains disappear before lunch. The Nasdaq fell 5.5%, AMD and Micron dropped about 17%, and the index slid into correction territory. A week later, the headlines have flipped: tech stocks now look cheap on forward P/E, the ratio most analysts quote when they say a market is "on sale."

That claim is true on paper. The tech sector's forward P/E fell to its lowest level since March 2020, below its own 25-year average. But a P/E is a fraction, and a cheap fraction can come from two very different places. Either the price fell, or the earnings forecast underneath it climbed fast. This time, both happened at once.

This guide explains what forward P/E measures, why it dropped so sharply this month, and the one question you should ask before treating a low number as a bargain. You will also see the math on how quickly "cheap" turns expensive if the earnings forecast slips.

What Happened in the November 5 Selloff

The selloff was broad and fast. According to CNBC's market coverage, the S&P 500 lost 4.36% to close at 7,353.73, the Dow dropped 1,833 points, and the Nasdaq fell 5.52%. That put the Nasdaq more than 10% below the record close it set in October, which is the textbook definition of a correction.

Every one of the 11 S&P 500 sectors closed lower. The heaviest damage landed on companies tied to the AI data center buildout: memory makers, chip designers and networking suppliers. The trigger CNBC cited was political. Investors worried that newly elected Democratic officials could slow data center construction, after Texas Governor-elect Gina Hinojosa told CNN the state should pause its data center push until protections are in place.

The next day, the Nasdaq bounced about 1%. Then the analysis started, and one note shaped how most people now talk about the drop.

Bank of America's read: multiples, not earnings

In a note covered by CNBC on November 6, Bank of America analyst Wamsi Mohan wrote that the selloff in AI hardware "has come from lower valuation multiples, not lower earnings estimates." His team's earnings forecasts for the group stayed at or above consensus.

In plain terms, investors did not decide these companies would earn less. They decided to pay less for each dollar the companies are expected to earn. That distinction is the whole story behind the P/E number, so it pays to understand exactly what the ratio measures.

Forward P/E Explained in Plain Numbers

Forward P/E is the share price divided by the earnings per share analysts expect over the next 12 months. If a stock costs $100 and analysts think it will earn $5 a share next year, its forward P/E is 20. You are paying $20 for every $1 of expected profit.

The trailing P/E uses the last 12 months of actual earnings instead. Trailing numbers are real but backward looking. Forward numbers look ahead, but they are only as good as the forecasts behind them.

Here is the index-level math from FactSet's November 6 Earnings Insight, which tracks the consensus forecast for every company in the S&P 500:

• Price on November 5: 7,353.73
• Forward 12-month EPS estimate: $415.82
• Forward P/E: 7,353.73 divided by 415.82 equals 17.7
• 5-year average: 19.8
• 10-year average: 19.1
• 25-year average: 16.4

So the market is cheaper than it has been for most of the past decade. It is still pricier than its long-run history, and nowhere near the 8.6 low FactSet recorded in November 2008. Whether 17.7 looks cheap depends entirely on which average you choose as your yardstick.

Why the P/E Fell So Far This Year

This is where the headline number gets misleading. FactSet reports that the S&P 500 started the year at a forward P/E of 22.0. Since then, the index price has risen 7.4%. Over the same stretch, the forward earnings estimate jumped 33.6%.

You can rebuild the result yourself. Take the starting P/E of 22.0, multiply by 1.074 for the price gain, and divide by 1.336 for the earnings gain. You land at 17.7. In other words, most of the "discount" came from analysts raising their profit forecasts, not from prices falling. The November 5 drop only finished the job.

The short-term picture tells the same story. Since September 30, FactSet says the index price fell 3.9% while forward EPS estimates rose 3.1%. Prices went one way, forecasts went the other, and the ratio dropped from 19.0 to 17.7 in five weeks.

The key point: a P/E falls when the "E" rises faster than the "P." That is only good news for you if the "E" turns out to be right.

Is Tech Actually Cheap? Check Where the Earnings Come From

FactSet found only two sectors trading below their 25-year average forward P/E on November 5: Energy, at 11.7 against 13.9, and Information Technology, at 17.3 against 20.0. For tech, it was the lowest reading since March 23, 2020, when the sector bottomed at 16.1 during the pandemic crash.

On its face, that looks like an opening. Then you check what is driving tech's earnings. The sector is reporting 69.2% year-over-year earnings growth for the third quarter. Semiconductors alone grew earnings 133%. Strip the chip industry out, and FactSet says tech's growth rate falls to 29.6%.

The cyclical trap in a low P/E

Chipmakers sell into boom and bust cycles. When demand peaks, profits balloon, and the P/E looks tiny because the denominator is huge. When demand cools, profits shrink, and the same stock price suddenly carries a much higher multiple. Seasoned investors call this buying cyclicals at peak earnings, and it has burned people in memory chips for decades.

That is exactly the risk the November 5 selloff priced in. Investors were not reacting to a missed quarter. They were questioning whether the data center spending behind those forecasts will last. If you want the background on how that spending gets funded, our breakdown of how AI stocks now run on borrowed money covers the debt side.

Worked Example: How "Cheap" Turns Expensive

Run the numbers on two scenarios. Neither assumes the price moves at all.

Scenario 1: the whole index

Start with the S&P 500 at 7,353.73 and forward EPS of $415.82, a P/E of 17.7. Now suppose analysts trim their forecasts by 10% over the next few months, to about $374.24. The price stays put.

• New P/E: 7,353.73 divided by 374.24 equals 19.7
• That is right back at the 5-year average of 19.8
• A 15% cut, to about $353.45, would push the P/E to roughly 20.8, above every long-run average FactSet lists

Flip it around. If forecasts hold and the P/E simply drifts back to its 5-year average of 19.8, the index would sit near 8,233. That is about 12% above the November 5 close. The upside case and the downside case both hinge on one input: the earnings estimate.

Scenario 2: a single chip stock

Picture a hypothetical chipmaker trading at $200 a share with forward EPS of $11.56. That is a P/E of 17.3, matching the tech sector. Its earnings just grew 133%, in line with the semiconductor industry, which means current profits are about 2.33 times last year's.

Now suppose demand cools and earnings slip back to last year's level. Divide $11.56 by 2.33 and you get about $4.96 a share. At the same $200 price, the P/E becomes about 40. Nothing about the stock changed except the forecast, and the "bargain" now costs more than double the sector's long-run average.

What This Means for Your Portfolio

If you own a broad index fund, you already hold these chip stocks, often in large weights. Our look at why your index fund is not as diversified as you think shows how a handful of names drive the whole index. A low P/E on a cyclical stock is a bet on the forecast, not a margin of safety. Use the signal this way:

1. Ask what moved, the P or the E. A falling price with steady forecasts is a different situation from a flat price with soaring forecasts.
2. Compare to more than one average. At 17.7, the S&P 500 sits below its 5-year and 10-year averages but above its 15-year, 20-year and 25-year ones.
3. Look at growth concentration. When one industry produces most of a sector's earnings growth, that sector's P/E depends on one industry's cycle.
4. Watch revisions, not just the ratio. FactSet counts 32 companies issuing negative fourth-quarter EPS guidance against 43 positive. If that balance tips, forward estimates will follow.
5. Keep your plan sized for a deeper drop. A correction is a 10% decline. A bear market starts at 20%, and the Nasdaq was already halfway there.

Frequently Asked Questions

What is a good forward P/E ratio for the S&P 500?

There is no fixed "good" number. FactSet puts the 5-year average at 19.8, the 10-year at 19.1 and the 25-year at 16.4. A reading near those averages suggests normal pricing, as long as the earnings forecasts behind it are realistic.

Why did the Nasdaq enter a correction in November?

The Nasdaq fell 5.52% on November 5, closing more than 10% below its October record. CNBC tied the drop to fears that newly elected officials could slow data center construction, which hit AI chip and hardware stocks hardest.

Is a low P/E ratio always a good sign?

No. A low P/E can mean a stock is undervalued, or that its earnings are at a cyclical peak and likely to fall. Chip stocks are the classic example, because their profits swing widely with demand.

What is the difference between forward P/E and trailing P/E?

Trailing P/E divides the price by the last 12 months of actual earnings. Forward P/E uses analysts' estimates for the next 12 months. FactSet puts the S&P 500's trailing P/E at 24.7 against its forward P/E of 17.7, a gap that reflects how much profit growth analysts expect.

Are tech stocks undervalued right now?

On forward P/E, the tech sector trades at 17.3 versus a 25-year average of 20.0. That only holds if analysts' forecasts hold. Semiconductors drove most of the sector's 69.2% earnings growth, so the valuation rests heavily on chip demand staying strong.

The Number to Watch Next

The November 5 selloff made tech look cheaper than it has in years, and the forward P/E confirms it on paper. But the ratio dropped mainly because earnings forecasts soared, led by a chip industry growing profits at 133%. That makes the next round of estimate revisions more important than the next day's price move.

When you see the next "stocks are cheap" headline, divide it in your head. Check what happened to the price, check what happened to the forecast, and ask what the ratio becomes if that forecast falls 10%. That habit takes thirty seconds and protects you from mistaking a peak for a bargain.

Disclaimer: This article is for informational purposes only and does not constitute financial advice. Always consult with a qualified financial advisor before making investment decisions. Past performance is not indicative of future results.