Following my first post about finding a book idea and testing it, let’s now look at how to calculate your writing metrics.

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Why writing metrics matter

Even with a strong idea, committing to a book is not trivial. And unlike a novel — where an author can afford to spend a decade crafting a chef-d’œuvre — a technical book operates under very different constraints.

If you take too long:

• your subject may become obsolete,
• the ecosystem may evolve beyond your initial premise,
• or another author may publish a similar book before you do.

If you work with a publisher, constraints become even more explicit. You will usually be given a schedule: a certain number of pages per month, a chapter due on a fixed date, or a full manuscript expected within a defined timeframe.

Whether you are self-publishing or working with a publisher, one thing remains true: you cannot plan realistically if you don’t know how fast you write.

That’s where writing metrics come in.

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Using exploratory chapters to measure yourself

In the previous post, I recommended testing your idea by writing a few exploratory chapters before committing fully. Those chapters serve another purpose: they allow you to extract three essential metrics:

• your writing speed
• your creative capacity
• your writing ratio

Most people focus on the first. In practice, the second is often more important.

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Metric #1: your writing speed

This metric is relatively easy to calculate. Once a writing session is over, take the number of pages (or words) you produced — depending on the metric you prefer — and divide it by the number of hours spent writing.

However, this metric will be different for each of your projects. Each project operates under different constraints and will have a different writing speed. For example:

• while writing The Art of Code, my speed was about half a page per hour;
• for another technical book written in my native language, it was almost twice that;
• story-driven writing tends to be faster.

Technical books are slower to write because they require constant verification, precision, and validation of ideas. Writing in a non-native language slows the process even further.

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Metric #2: your creative capacity

This is a metric I didn’t even know existed before I fully committed to writing a book.

During my early sessions, something kept happening. Two or three hours in, my creativity would suddenly drop — sometimes quite brutally. Writing became harder. The result felt flat and less engaging. Everything slowed down, frustration increased, and progress stalled.

After seeing this pattern repeat several times, I had to accept a simple fact:
I have a creative limit of about three hours.

At first, I thought this was low. I had this romantic image of writers spending entire days immersed in their books, writing from dawn to dusk. Compared to that, three hours felt underwhelming.

But after digging a bit deeper, I realized it was actually average.

Creative work is cognitively expensive. Most people can sustain deep creative effort for two to four hours per day. Probably closer to two after an intense workday, and closer to four on a quiet weekend morning.

That creative capacity applies mainly to writing. Other necessary activities, such as researching or writing code, do not tap into it in the same way. This allows you to keep working even once you’re out of creative juice.

While writing, pay attention to your creative capacity. Notice when writing becomes more laborious and your pace starts to slow down, and use that to determine your creative limit.

Why this metric changes everything

Let’s say you’ve measured your writing speed at one page per hour. It might be tempting to plan an eight-hour writing session on a Sunday and expect eight pages. That plan is almost guaranteed to fail if your creative capacity is only four hours. You won’t get eight good pages. You’ll get four solid ones — and four hours of struggle.

This is why creative capacity is a hard constraint. Your schedule must be built around it, not against it.

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Metric #3: your writing ratio

When you write a technical book, not all of your working time is spent writing. You will need to:

• read documentation,
• explore tools or frameworks,
• write and test code,
• build models,
• integrate feedback from reviewers or editors.

All of this work is necessary. But none of it directly produces pages — and it significantly slows down apparent progress. This is why a third metric matters: your writing ratio. The writing ratio is the percentage of your total working time that is actually spent writing text.

For example, when working with a publisher, only about 70% of my time was spent writing. This means that even with a writing speed of half a page per hour, an average three-hour writing session did not produce one and a half pages, but closer to one page.

Of course, this is not a metric you can calculate on a per-session basis. Some sessions will be entirely dedicated to research or writing code and will produce zero pages. Others will focus almost exclusively on writing and may produce three pages. This is why the writing ratio is the hardest metric to estimate.

My approach is the following:

• first, calculate writing speed using sessions focused exclusively on writing;
• then, look at a larger time span — a week or a month — and measure how much was actually written;
• finally, compare the observed output with what would have been expected based on writing speed alone, and calculate the ratio.

Those three metrics should not become a source of stress. One or two months are enough to get a rough estimate, which you can then refine as the project evolves.

In the next post, I’ll show how to use these metrics to plan realistic writing sessions.