How to Calculate an Article's Reading Time

An article's reading time is a small but useful interface detail. It tells readers how much time they will need and helps them decide whether to start reading now.

For example, you can display this beside the heading:

Reading time: 4 minutes

The calculation does not require complex analytics. Estimate an average reading speed and account for the amount of content.

How to Calculate Reading Time

You can use the following average reading speed:

1500 characters per minute

The basic formula is:

Number of characters / 1500

If the article includes images, viewing them also takes time.

For each image, add:

0.2 minutes

The complete formula is therefore:

Reading time =
Number of characters / 1500
+
Number of images × 0.2

Worked Example

Suppose the article contains:

• 4,315 characters;
• 2 images.

First, calculate the time needed to read the text:

4315 / 1500 = 2.87

Then add time for the images:

0.2 × 2 = 0.4

The result is:

2.87 + 0.4 = 3.27 minutes

The displayed reading time can be:

3 minutes

How to Round the Result

Use a simple rounding rule to avoid setting overly optimistic expectations.

1. Take the calculated reading time.
2. Check its fractional part.
3. If it is below 0.3, keep the current whole-number value.
4. If it is 0.3 or higher, round up to the next whole number.

For example:

3.27 → 3 minutes
3.30 → 4 minutes
3.85 → 4 minutes

This small allowance accommodates people who read more slowly than average.

Another Example

Suppose the article has 4,350 characters and the same 2 images.

Calculate the text reading time:

4350 / 1500 = 2.9

Add the images:

2.9 + 0.4 = 3.3

The fractional part is 0.3, so round up:

4 minutes

Calculation Algorithm

When briefing a developer, describe the algorithm as follows:

1. Count the characters in the article.
2. Divide the count by 1,500.
3. Count the images.
4. Add 0.2 minutes per image.
5. Check the fractional part of the result.
6. If it is 0.3 or higher, round the time up.
7. Display the result beside the article heading.

Do You Need Analytics?

You could calculate average reading time from actual visitor behaviour, but that is usually excessive for this feature.

Time spent on a page does not necessarily equal time spent reading.

A visitor might:

• Open the article and become distracted;
• Spend a long time examining images;
• Switch to another tab;
• Read only part of the article;
• Return to the article later.

Accuracy to within a few seconds is therefore unnecessary.

The main purpose of the reading-time indicator is to give readers a rough idea of the amount of material.

Summary

A simple reading-time estimate needs only three parameters:

• A reading speed of 1,500 characters per minute;
• An extra 0.2 minutes per image;
• Rounding up if the fractional part is 0.3 or higher.

This is enough to show a clear estimate such as ‘3 minutes’ or ‘7 minutes’ without complex analytics or additional tracking.