Choosing the right Bathmate size is one of the most important steps before buying a penis pump. A pump that is too small may feel restrictive or uncomfortable, while a chamber that is unnecessarily large may make it more difficult to achieve an effective seal and pressure.

Fortunately, choosing a Bathmate size does not need to involve guesswork. Bathmate bases its sizing system primarily on two measurements: erect penis length and erect girth.

In this guide, we explain how to measure yourself, compare Bathmate sizes from 3 to 11, understand what to do when your measurements fall between two sizes and look at the special case of the HydroXtreme 7 Wide Boy.

The goal is simple: choose a chamber with enough room for comfortable use without automatically selecting a larger pump than you need.

Bathmate Size Guide at a Glance

These measurements are based on Bathmate's official sizing guidance. Manufacturer specifications and available models may change, so always check the latest product information before ordering.

1. Why Does the Correct Bathmate Size Matter?

It may be tempting to assume that a larger penis pump is automatically the better choice because it provides more room. With vacuum pumps, however, bigger is not necessarily better.

The chamber needs to fit closely enough to create an effective seal while still providing sufficient room for comfortable use.

If the Pump Is Too Large

An unnecessarily large chamber may make it more difficult to create and maintain the pressure the pump is designed to produce. It may also feel less stable against the body.

If the Pump Is Too Small

A chamber that is too short or narrow may become uncomfortable and may not provide enough space during use.

This is why Bathmate sizing should be based on your actual measurements rather than choosing a model simply because its number is larger or because it looks more powerful.

If you are new to penis pumps and want to understand how they work before choosing a specific model, read our complete guide to penis pumps, their purpose and what to know before buying.

2. Measure Before You Choose a Bathmate

Before comparing models, take two measurements:

• Erect length
• Erect girth

For consistent results, measure while fully erect.

3. How to Measure Erect Penis Length

Use a ruler or measuring device and measure along the top side of the penis.

Step by Step

1. Measure when fully erect.
2. Place the ruler along the top of the penis.
3. Start at the base, where the penis meets the pubic area.
4. Measure in a straight line to the tip.
5. Record the result in centimetres or inches.

For consistency, use the pubic bone as the reference point at the base. If necessary, gently press the ruler through the soft tissue at the base until it reaches the pubic bone.

Avoid measuring from underneath or along the side because doing so can produce a different result and make comparison with the sizing chart less reliable.

4. How to Measure Erect Girth

Girth means the circumference around the penis rather than its width from one side to the other.

Step by Step

1. Measure when fully erect.
2. Use a flexible measuring tape.
3. Wrap it around the thickest part of the shaft.
4. Keep the tape comfortably against the skin without pulling it tightly.
5. Record the circumference.

If you do not have a flexible measuring tape, wrap a piece of string around the shaft, mark where the ends meet and then measure that section against a ruler.

5. Use Both Length and Girth

One of the most common mistakes when choosing a penis pump is looking only at length.

For example, two people may both have an erect length of 15 cm but have considerably different girth measurements. A chamber that provides enough length for both users may not provide the same amount of width.

Always compare both measurements with the Bathmate sizing chart.

6. Understanding Bathmate Sizes

Bathmate Size 3

Size 3 is intended for an erect length of up to approximately 3 inches or 7.6 cm, with erect girth up to approximately 6 inches or 15.2 cm.

It is the smallest size in Bathmate's current general sizing system.

Bathmate Size 5

Size 5 is designed for an erect length of approximately 3–5 inches or 7.6–12.7 cm, with girth up to approximately 6 inches or 15.2 cm.

This size overlaps partly with Size 6, so your girth and exact position within the length range should also be considered.

Bathmate Size 6

Size 6 covers an erect length of approximately 4–6 inches or 10.2–15.2 cm, with maximum girth of approximately 6.5 inches or 16.5 cm.

Because its range overlaps with Sizes 5 and 7, users close to either end of the length range should pay particular attention to girth.

Bathmate Size 7

Size 7 is intended for an erect length of approximately 5–7 inches or 12.7–17.8 cm and girth up to approximately 6.5 inches or 16.5 cm.

This is a good example of why the model number should not be used alone. Someone whose length fits Size 7 still needs to check whether their girth is within its recommended range.

Bathmate Size 8

Size 8 covers approximately 6–8 inches or 15.2–20.3 cm of erect length and up to approximately 7 inches or 17.8 cm of erect girth.

It provides additional length and girth capacity compared with Size 7.

Bathmate Size 9

Size 9 is intended for an erect length of approximately 7–9 inches or 17.8–22.9 cm, with girth up to approximately 7.5 inches or 19.1 cm.

If your length is near the lower end of this range, do not choose Size 9 simply because you expect to need more room. Compare your measurements with the smaller overlapping size first.

Bathmate Size 11

Size 11 is the largest option in Bathmate's general sizing chart. It is designed for approximately 9–11 inches or 22.9–27.9 cm of erect length and up to approximately 8.5 inches or 21.6 cm of girth.

Because this is a particularly large chamber, it should be selected according to actual measurements rather than simply as an upgrade from a smaller model.

7. What If Two Bathmate Sizes Fit?

This can easily happen because several Bathmate sizing ranges intentionally overlap.

For example:

• Sizes 5 and 6 overlap between 4 and 5 inches of length
• Sizes 6 and 7 overlap between 5 and 6 inches
• Sizes 7 and 8 overlap between 6 and 7 inches
• Sizes 8 and 9 overlap between 7 and 8 inches

An overlap does not mean that one size is automatically wrong.

Instead, consider:

• Your exact erect length
• Your erect girth
• How close you are to the maximum measurement of the smaller size
• The manufacturer's current recommendation for the specific Bathmate model

Do not automatically size up whenever two models appear possible. An oversized chamber is not necessarily more comfortable or more effective.

8. What If Your Length Fits but Your Girth Does Not?

Girth should not be ignored simply because your length falls comfortably within a particular size range.

For example, your erect length may fall within the Size 7 range while your girth exceeds the listed maximum for Size 7. In that situation, Size 7 should not automatically be considered suitable based on length alone.

Compare your girth with the next available options and check the manufacturer's current sizing guidance before ordering.

This is also one of the situations in which the HydroXtreme 7 Wide Boy may be worth considering.

9. What Is the Bathmate HydroXtreme 7 Wide Boy?

Bathmate offers the HydroXtreme 7 Wide Boy as a wider variation within its HydroXtreme range.

It is designed for users interested in the Size 7 category but who may prefer or require a wider chamber.

However, Bathmate's general public sizing chart does not currently provide a separate numeric length-and-girth range for the 7 Wide Boy.

For that reason, it is better not to rely on unofficial measurements or assume that a particular girth automatically requires this model.

If you are considering the 7 Wide Boy:

• Measure your erect length and girth first
• Compare your measurements with the standard Size 7 range
• Check Bathmate's latest HydroXtreme sizing information
  

10. Bathmate Size Does Not Mean Power Level

A common misunderstanding is that a Bathmate Size 9 is somehow a more powerful version of Size 7 simply because it has a higher number.

The size number primarily identifies chamber dimensions intended for different body measurements. It should not be treated as an intensity or performance rating.

Your first priority should therefore be fit, not choosing the highest number available.

11. Do Not Choose a Bigger Size Just to “Grow Into It”

If your current measurements fit comfortably within one size, choosing a substantially larger chamber because you hope to grow into it later may reduce the quality of the initial fit.

A correctly sized chamber is important because an unnecessarily large pump may make it more difficult to achieve the intended seal and pressure.

Choose according to your current erect measurements.

If your measurements later change enough that you approach the limits of your existing chamber, you can compare the available sizes again.

12. Common Bathmate Sizing Mistakes

Measuring While Flaccid

Flaccid size can vary considerably depending on temperature, stress and other factors. Bathmate sizing is based on erect measurements, so measure when fully erect.

Measuring Only Length

A correct length measurement does not guarantee that the chamber will also accommodate your girth.

Measuring Girth as Width

Girth means the full circumference around the shaft. Do not measure only from one side to the other.

Automatically Choosing the Larger Option

If two ranges overlap, the larger number is not automatically the better choice.

Ignoring Current Manufacturer Guidance

Product ranges and specifications can change. Old forum posts, images and retailer charts may no longer reflect Bathmate's current recommendations.

Guessing Your Measurements

Even a difference of a centimetre or two can place you closer to the boundary between two sizes. Measuring takes very little time and removes much of the uncertainty.

13. Quick Bathmate Size Comparison

This table is intended as a quick reference. When ranges overlap, use the complete Bathmate sizing chart and compare girth rather than choosing from length alone.

14. Choosing Between Hydromax and HydroXtreme

Size is only one part of choosing a Bathmate pump. Once you know which chamber dimensions match your measurements, you can compare the available Bathmate product ranges.

Different Bathmate ranges offer different features, controls and available chamber sizes.

A practical order for choosing a Bathmate is:

1. Measure your erect length.
2. Measure your erect girth.
3. Identify the Bathmate sizes that accommodate both measurements.
4. Compare which Bathmate ranges offer the appropriate size.
5. Choose between the available models according to features and budget.

This approach is better than choosing a particular Bathmate model first and then trying to make its chamber size fit your measurements.

15. What If You Are Exactly at the Maximum Size?

If one or both measurements are very close to the listed maximum for a particular size, take additional care before ordering.

Measure again to make sure the result is accurate and compare the next size as well. Because Bathmate ranges overlap, more than one option may be possible.

Do not make the decision from length alone. If you are close to the maximum in both length and girth, checking the latest manufacturer guidances before ordering can help you avoid choosing a chamber that feels unnecessarily restrictive.

16. How Accurate Do Your Measurements Need to Be?

You do not need laboratory-level precision, but careful measurement is worthwhile.

For the most consistent result:

• Measure when fully erect
• Use the same measuring method each time
• Measure length along the top
• Measure girth around the thickest part of the shaft
• Take the measurement again if the first result seems uncertain

If your readings vary slightly, use them to understand where you fall within the manufacturer's range rather than rounding aggressively toward a different size.

How to Use a Bathmate Safely

Choosing the right size is only part of using a penis pump correctly. Once you have selected an appropriate chamber, it is equally important to understand how to create vacuum gradually, how to release pressure and when to stop using the pump.

If you are using a penis pump for the first time, read our guide on how to use a penis pump safely and correctly before your first session.

Always follow the instructions supplied with your specific Bathmate model rather than applying one universal pressure level or session duration to every pump.

Frequently Asked Questions About Bathmate Sizes

Should I measure erect or flaccid?

Use your fully erect measurements when comparing your length and girth with the Bathmate size chart.

Does Bathmate size refer only to penis length?

No. Each Bathmate size corresponds to a recommended erect length range, but maximum girth is also listed. Both measurements should be considered.

Should I size up if I am between two Bathmate sizes?

Not automatically. Bathmate ranges overlap, so compare both your erect length and girth and check the current recommendation for the model you are considering.

Is a bigger Bathmate pump better?

No. The goal is an appropriate fit. A chamber that is unnecessarily large may be more difficult to seal effectively, while a chamber that is too small may feel restrictive or uncomfortable.

What is the difference between Bathmate Size 7 and Size 9?

Size 7 is listed for approximately 5–7 inches / 12.7–17.8 cm of erect length and up to 6.5 inches / 16.5 cm of girth. Size 9 is intended for approximately 7–9 inches / 17.8–22.9 cm of erect length and up to 7.5 inches / 19.1 cm of girth.

What is the Bathmate 7 Wide Boy?

The HydroXtreme 7 Wide Boy is a wider version available within the HydroXtreme range. Because Bathmate's general public size chart does not currently list a separate numeric girth range for this model, check the latest manufacturer information before selecting it.

Can I choose my Bathmate size using only girth?

No. Compare both erect length and erect girth.

Can I choose a larger pump because I expect my size to increase?

It is better to choose according to your current measurements. An unnecessarily large pump may not fit or seal as effectively as an appropriately sized chamber.

For the manufacturer's latest measurements, you can also consult the official Bathmate size guide.

Final Thoughts

Choosing the right Bathmate size comes down primarily to two measurements: erect length and erect girth.

Measure carefully, compare both values with the size chart and do not assume that a larger chamber is automatically better. Because several Bathmate ranges overlap, some users may fit more than one size, which makes considering both dimensions particularly important.

If you are close to a size limit, considering the HydroXtreme 7 Wide Boy or simply unsure which option to order, check Bathmate's latest guidance before purchasing.

A few minutes spent measuring before ordering can make choosing your Bathmate much simpler and help you find a chamber with an appropriate combination of space, comfort and fit.

Sizing information in this guide is based on Bathmate's official sizing guidance available at the time of publication. Manufacturer specifications and available models can change. Always consult current product information before purchase.

LuvMechanics is an independent retailer. Bathmate is a trademark of its respective owner. Sizing information is based on Bathmate's publicly available official sizing guidance and was last checked in August 2026. Manufacturer specifications may change.