How Erections Work

Erections happen in response to sexual arousal. Learn more about how and why.

For many people, erections are a part of day-to-day life. Erections happen when the penis gets hard and usually stands outward or upward. This happens most often in response to sexual arousal, but sometimes it can happen for no reason at all, particularly during puberty and during the teen years. Erections can go away after ejaculation or on their own. 

Although many people experience erections, there’s a lot most people don’t understand. The ability to get and maintain an erection can cause stress for some people.

Here’s what you should know about how erections work, including how hard an erection should be, erectile problems, and tips for better erections. 

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Anatomy of an Erection

An erection occurs when blood flows into the penis faster than it flows out. This causes the tissue in the penis to swell up and become hard. To understand how this happens, it’s helpful to know a bit more about the anatomy of the penis

The shaft of the penis has two different types of tissue that change when you get an erection:

  • The corpus cavernosa: Also known as erectile tissue. This tissue runs in two columns, along the sides of the penis. The corpus cavernosa is made up of muscle, collagen, and fiber that surround empty areas. When a person is sexually aroused, blood rushes into these empty areas, filling them up and causing the penis to stand erect. Blood vessels at the base of the penis constrict, keeping the blood in the corpus cavernosa. If there is venous leakage (which can occur after pelvic surgery) this process can be difficult and there can be venous leakage.
  • The corpus spongiosum: A similar line of tissue that runs on the underside of the penis and surrounds the urine channel called the urethra. This area doesn’t become as enlarged as the corpus cavernosa, and it maintains a continuous blood flow in and out while a person has an erection.

The tunica albuginea is a band of fiber near the base of the penis that constricts during an erection, compressing the veins that would normally allow blood to flow out of the penis. As sexual arousal passes, the tunica albuginea relaxes, allowing blood to flow out of the penis. As this happens, the penis becomes flaccid again.

Stages of an Erection 

Many people with penises are familiar with the ways that an erection progresses. Most people start with a flaccid—or soft—penis, which gradually grows swollen before becoming fully erect. 

Scientifically, there are five stages to an erection. They are:

  • Latent: During this phase, impulses from the brain signal sexual arousal, and the penis relaxes, allowing the corpus cavernosa to begin filling with blood. 
  • Tumescence: At this point, the penis is slightly swollen. The penile arteries become enlarged, allowing more blood flow into the penis. 
  • Erection: The tunica albuginea restricts blood from exiting the penis, increasing blood pressure in the penis and making the penis stand erect. 
  • Rigidity: As the penis continues to become more engorged, the veins that allow blood to exit the penis become more restricted, causing maximum hardness in the erection. During sexual activity, this stage occurs just before climax. 
  • Detumescence: After climax—or when the arousal has passed—the tunica albuginea relaxes, allowing blood to flow out of the penis. The penis returns to its normal, flaccid state. 

After having an erection and climaxing, many people have a refractory period, during which they can’t get another erection even if they’re stimulated. This can be as short as 15 minutes, or as long as a day or more.

How Hard Is a Normal Erection? 

An erection that is hard enough to allow for penetrative sex is considered a normal, healthy erection. This usually occurs at the erection and rigidity stages listed above. 

Scientists have a more precise answer: in most men, the pressure in the penis during an erection reaches 100 mmHg, a measurement of pressure. However, when it comes to evaluating your own erection, don’t worry about the numbers: if your penis is hard enough to penetrate a partner and reach orgasm, your erection is considered normal and healthy. 

Factors Influencing Erections

Erections are a normal and common bodily process, but in many ways they are out of the control of the person experiencing them. Having too many or too few erections can be embarrassing and take a mental toll. 

Erections During Puberty

During puberty, it’s normal for people to experience erections for seemingly no reason at all. It’s very common during male puberty to get involuntary erections, that can happen at what seems like the worst time.

Unfortunately, there’s little that boys can do to avoid this, other than waiting for their hormones to settle down with time. 

Erectile Problems

The more common concern after puberty is erectile problems. Erectile dysfunction is generally diagnosed when a person consistently has trouble getting or maintaining an erection long enough to have penetrative sex and climax.

Even without erectile dysfunction, it’s entirely normal for people to experience occasional trouble with erections. This often has nothing to do with them or their partner but can be caused by:

  • Age: People over the age of 40 are much more likely to have trouble getting or maintaining an erection. 
  • Health conditions: A strong erection requires healthy blood flow. Health conditions that affect the cardiovascular system, including diabetes, obesity, inflammatory conditions, low testosterone, and heart disease can all impact your ability to get or maintain an erection. 
  • Substance use: Certain drugs (recreational or prescribed) and even alcohol can make it difficult for your body to have an erection. 
  • Stress: Mental and emotional stressors can detract from your ability to get an erection. Conditions like depression or anxiety, arguments with your partner, or a looming work deadline can make it difficult to get hard. 

Tips for Better Erections

If you or your partner are unsatisfied with your erections, start by asking yourself what you would like to change. If you are having trouble getting or maintaining an erection that is hard enough for penetrative sex, you should speak with your doctor. Although erectile dysfunction is very common, only 10% of men who experience it seek medical treatment. 

If you want a more firm erection or a longer-lasting erection, experiment with different sexual activities. More foreplay, or switching positions, might help with any issues that you’re encountering. 

Overall, practicing good health can help you get and maintain strong erections. This includes:

  • Exercising regularly
  • Healthy diet
  • Avoiding alcohol, drugs, and smoking
  • Decreasing stress where possible
  • Maintaining a healthy emotional relationship with your partner or partners
  • Talking openly about sexual satisfaction and any sexual anxieties


An erection is when the penis hardens and protrudes away from the body. If you’re getting erections too often or not often enough, you might wonder if something is wrong with you. 

However, in most cases, your erection is entirely healthy. If you can maintain an erection that is hard enough for penetrative sex, you are likely experiencing a “normal” erection. If you regularly have trouble getting or maintaining an erection, speak with a healthcare provider, who can help you treat the problem. 

Remember, that sexual health is part of overall health. Keeping yourself physically, mentally, and emotionally healthy will help ensure that you get an erection that you and your partner are both satisfied with.

4 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Panchatsharam, Pranau K. Erection physiology.

  2. Chesapeake Urology. The anatomy of the penis — how an erection occurs

  3. Urology Care Foundation. What is erectile dysfunction?

  4. Nemours, Teens Health. Is it normal to get erections?

By Kelly Burch
Kelly Burch is has written about health topics for more than a decade. Her writing has appeared in The Washington Post, The Chicago Tribune, and more.