What happened

Nucor, the largest steelmaker in the United States, is at $249.87, down 5.76% (−$15.27) as reported by StockAnalysis at 10:50 am ET. The trigger landed Thursday after the close: Nucor guided third-quarter earnings to $5.55–$5.65 per diluted share. Analysts sat around $6.17–$6.20. That gap, roughly 55 to 65 cents a share, is the whole move.

Why it moved, when the number itself looks fine

Here is what the headline buries. The guide is higher than the quarter before it — Q2 was $5.04 reported, $4.84 adjusted — and more than double the $2.63 of the same quarter in 2025. It is also cleaner, because Q2 carried $130 million of one-off cash refunds on past raw-material purchases and a $61 million non-cash gain ($0.20 a share) from marking up Nucor's stake in fusion startup Helion. Neither repeats in Q3.

So Nucor guided to more profit from a cleaner base, and the stock fell anyway. The only comparison that mattered was the estimate. Inside the guide: Steel Mills rise on higher prices and steady volumes, clipped by higher product costs; Steel Products rise on volume and price; Raw Materials fall on lower pricing and shipments. Add higher corporate expense with no Helion gain to offset it, and you land short of $6.20.

The bit worth learning: Nucor sells steel, but it earns a spread

Nucor runs electric arc furnaces — it melts recycled scrap rather than smelting iron ore. Its profit is not the steel price; it is the gap between what it sells steel for and what it pays for scrap. In Q2 the average mill price was $1,145 a ton, up 7% on the quarter, while scrap and substitute costs ran $422 a gross ton, up 4%. Both rose. The spread decides the quarter, which is why a tight steel market does not automatically mean a bigger number.

And it is tight. Steel Market Update had hot-rolled coil at $1,240 a short ton on 15 September, up $60 on the month, and quoted a Midwest service centre: "we've got huge OEMs begging for steel." Nucor shipped a record 7.1 million tons in Q2 at 91% utilisation, up from 86% in Q1.

The business

Three segments, nowhere near equal. On Q1 2026 numbers: Steel Mills $1,128m (bars, beams, sheet, plate, tubing, joists, deck), Steel Products $285m (joist and rebar fabrication, building systems, overhead doors, fasteners), Raw Materials $45m (scrap brokerage and processing, ferro-alloys). The segment guided down today is the smallest by a wide margin. Nucor also sells fabricated steel into data centres via Nucor Data Systems.

Valuation

Market cap $56.69bn on a trailing P/E of 21.17, forward P/E 11.37, price-to-book 2.72 and EV/EBITDA 11.36, per StockAnalysis. Peer Steel Dynamics — same scrap-fed model, $33.91bn market cap — trades at a trailing P/E of 21.47, forward 10.98, and is down 3.57% today. Over five years Macrotrends puts Nucor's quarterly P/E between 3.08 (Q2 2022) and 21.41 (Q1 2025). The distance between 21 trailing and 11 forward is the market assuming earnings roughly double from here; today shaved a piece off that.

Who it touches

• Steel Dynamics — identical scrap-to-steel spread, so Nucor's cost message reads across almost line for line.
• Cleveland-Cliffs — blast-furnace and ore-fed, so rising scrap bites it far less. We decoded its own 15% day here.
• Scrap yards and recyclers — $422 a gross ton is Nucor's cost line and their revenue line.
• Steel buyers — data centres, construction, autos. US mill shipments fell 3.7% from June to July, but year-to-date through July ran 5.3% above 2025. More movers here.

What to watch

Nucor reports 26 October after the close, call 27 October at 10:00 am ET (calendar). One number to keep: Nucor has already repurchased about 2.03 million shares this quarter at an average $247.04 — within a few dollars of where it trades right now.

The one thing that flips this: if hot-rolled coil holds near $1,240 into Q4 while scrap eases, the spread widens and today's guide is the low point. If scrap climbs alongside steel, the same squeeze returns in January.

As of 10:50 am ET, 18 September 2026. Sources: Nucor, StockAnalysis, Investing.com, Traders Agency / Steel Market Update, SteelOrbis, Macrotrends. For discussion and education only — not investment advice. Verify before acting.