hosuukei de hosuu wo kirokusuru.

It is read:

ほすうけい で ほすう を きろくする。

• 歩数計（ほすうけい） = pedometer / step counter
• 歩数（ほすう） = number of steps
• 記録する（きろくする） = to record

Because 歩数計 is made from:

• 歩数（ほすう） = step count
• 計（けい） = meter / measuring device

So 歩数計 literally means step-count meter.

That is why the first two words look and sound similar:

• 歩数計 = the device
• 歩数 = the thing being counted/recorded

Here, で shows the means or tool used to do something.

So:

• 歩数計で = with a pedometer / using a pedometer

In this sentence, the pedometer is the instrument used to record the step count.

Because 歩数計 is not the direct object here. It is the tool used for the action.

The direct object is 歩数, marked by を:

• 歩数を記録する = record the number of steps

So the structure is:

• 歩数計で = using a pedometer
• 歩数を = the step count
• 記録する = record

を marks the direct object of the verb.

Here, the verb is 記録する (to record), and the thing being recorded is 歩数 (step count).

So:

• 歩数を記録する = to record the number of steps

記録する is the dictionary/plain form.

This form is commonly used in:

• dictionary entries
• headings
• instructions
• labels
• neutral written style
• casual speech

If you wanted a more polite sentence, you could say:

• 歩数計で歩数を記録します。

Both mean basically the same thing, but 記録します is more polite.

Yes, Japanese often leaves out the subject when it is obvious or unimportant.

So this sentence does not explicitly say who is recording the steps.

Depending on context, it could mean:

• I record my steps with a pedometer
• You record your steps with a pedometer
• One records step count with a pedometer
• A pedometer records step count

Japanese often relies on context instead of stating the subject every time.

Yes, it can depending on context, but the phrasing is a little ambiguous in isolation.

Because で usually marks a tool/means, many learners will first understand it as:

• record the step count using a pedometer

But in practical contexts, especially in short explanatory phrases, it can also be understood as describing what a pedometer does.

If you wanted to make the pedometer clearly the subject, you might use:

• 歩数計が歩数を記録する。

Here, が makes 歩数計 the subject.

Japanese is normally written without spaces. So this sentence would usually appear as:

歩数計で歩数を記録する。

Spaces are often added in learning materials to make the structure easier to see.

Yes. 記録する is a noun + する verb.

• 記録（きろく） = record / recording
• する = to do

Together:

• 記録する = to record

This pattern is very common in Japanese. For example:

• 勉強する = to study
• 運動する = to exercise
• 確認する = to confirm

The sentence follows the typical Japanese pattern of putting the verb at the end:

• 歩数計で = with a pedometer
• 歩数を = steps / step count
• 記録する = record

So the structure is roughly:

[tool] + [object] + [verb]

Japanese word order is often more flexible than English, but the verb usually comes last.

Yes. In many contexts, 歩数 can be translated naturally as:

• steps
• number of steps
• step count

The most natural choice depends on the situation.

For example:

• 歩数を記録する = record your steps
• record the number of steps
• record step count

All are reasonable translations.

計（けい） often means meter, gauge, or measuring device in compounds.

Examples:

• 温度計（おんどけい） = thermometer
• 体温計（たいおんけい） = body thermometer
• 電圧計（でんあつけい） = voltmeter
• 歩数計（ほすうけい） = pedometer

So 歩数計 literally means a device that measures/counts steps.