Book-to-Bill Ratio

The book-to-bill ratio is a simple metric from industry. It divides the sum of new orders by the sum of billings for a period, usually a quarter. If a chip-manufacturer’s customer orders for 120 million euros while the company ships for 100 million, the ratio stands at 1.2. A value above 1 means: the order backlog is growing. A value below 1 means: the company is working off more than is coming in new. The English name comes from “to book” (recording an order) and “to bill” (issuing an invoice).

What the number reveals about the coming quarters

Revenue always looks backward. It shows what a company has already delivered, often based on orders from the previous year. The book-to-bill ratio, by contrast, looks forward. It says how full the order books are becoming right now. That’s why stock prices sometimes react more strongly to this metric than to profit.

This is especially important in industries with long lead times. A chip-manufacturing machine is ordered and only delivered one to two years later. Today’s ratio thus reveals what business will look like in two years. In the semiconductor industry, this metric has been considered the most important sentiment indicator for decades. If it falls below 1 for several quarters in a row, analysts speak of a downturn in the cycle.

It’s important to distinguish this from the order backlog. The order backlog is the absolute pile of unfinished work, measured in euros. The book-to-bill ratio, by contrast, is a rate of change: it shows whether this pile is growing or shrinking. Both figures complement each other but do not replace one another.

From order intake to metric

The calculation itself is trivial: order intake divided by revenue in the same period. The harder question is what actually counts as an order. Companies define this differently. Some record only bindingly signed contracts, others also letters of intent. Because there is no uniform rule, two companies can only be compared directly to a limited extent.

It therefore makes most sense to compare a company with itself over time. Analysts look at the trend over four to eight quarters, not at a single value. A single outlier can have harmless causes. A major customer orders its annual requirement all at once, and the ratio jumps to 1.4, without anything actually changing in the business.

A typical misconception: a high ratio is read as purely good news. But it can also indicate delivery problems. If a plant is at a standstill and barely shipping, the denominator shrinks — the ratio rises even though the company has a problem. Conversely, a record quarter in deliveries pushes the metric down. So one must always look at both figures individually, not just their ratio.

Chip quarterly results and the AI boom

The metric appears most often in reports about semiconductor companies and equipment makers. Manufacturers of lithography machines, networking technology, or data-center servers regularly cite it in their quarterly reports. Industry associations also publish aggregated figures for entire markets. Anyone reading business news about the chip industry will almost inevitably stumble across it.

In the context of artificial intelligence, the figure has recently received particular attention. The construction of data centers is driving orders for specialty chips, cooling technology, and power supply. A persistently high book-to-bill ratio among these suppliers is seen by many as evidence that demand is real and not merely announced. If it falls, discussions about the end of the boom start immediately.

For retail investors, the metric is a useful but blunt compass. It’s easy to understand and quick to calculate. However, it says nothing about prices, margins, or cancellations. An order can be canceled before it ever turns into an invoice — this happens more often, especially in uncertain times.