Erection: how hard is hard

Doctors grade erections on a four-step scale, cocks grow by very different amounts, and the busiest erections of the day happen while you sleep

Hard is not a yes or no. Every man who has tried to put on a condom at the wrong moment knows there are stages: a bit bigger, bigger but bendy, good enough, and the real thing. Medicine noticed too, and turned those stages into a four-point scale that fits on a sticky note.

This chapter is about that scale, about how much a cock grows on the way up, and about the erections you never see, because they happen while you sleep.

How hard is hard

The Erection Hardness Score asks one question and offers four answers. It was validated in 2007 on 307 men taking part in a drug trial for erectile problems, and it held up well: men gave the same answers when asked twice, and the score tracked the longer questionnaires urologists use. Here are the four levels, in plain words.

Some versions add a zero for no change at all. The angle in the drawings is only there to make the levels easy to tell apart: how high a cock points depends on more than hardness, as the chapter on angle explains.

Notice where the line falls. The scale was written around one practical test, penetration, and it does not care which hole or whose. For a top the jump from 2 to 3 is the one that matters. For a bottom, or for anyone whose evening does not involve penetrating anybody, a 2 can be a perfectly good erection, and nobody hands out a score anyway.

Growers and showers

The gay world has its own vocabulary for how much a cock changes on the way up. A shower looks much the same soft and hard, a grower seems to come out of nowhere. The difference turns out to be real, and measurable.

In 274 men measured soft and then after an injection that gave them a full erection, the median gain in length was 4 cm1.6 in, ranging from 1 cm0.4 in to 7 cm2.8 in. Using that median as the cut-off, about a quarter were growers, adding 5.3 cm2.1 in on average, and three quarters were showers, adding 3.1 cm1.2 in. Soft length did not predict which group a man fell into. Being younger did, and the growers also ended up longer when hard.

A 2026 study of 420 men took a less arbitrary route, letting the data sort men into groups instead of picking a line. It found distinct growth profiles and linked them to how the tough outer sheath of the erectile tissue behaves as it fills. In other words, grower or shower is not locker-room folklore, it is plumbing. Both studies looked at men attending clinics for erection problems, so they are not a random slice of the population. The full story is in Grower or shower.

The erections you sleep through

Your cock is busier at night than you are. Sleep-lab studies since the 1970s have recorded erections that come and go through the night, tied to the dreaming phase of sleep, REM. The classic study on young men is usually summarised as three to five episodes a night, each lasting around half an hour, although those figures reach us through later summaries rather than the original tables.

Morning wood is simply the last of the series: you wake up during or just after a REM phase and catch the erection that was already happening. A full bladder is the popular explanation, but it is not the main driver.

Doctors put those night shifts to work. Because sleep erections happen without desire or nerves, a man who has them but struggles awake is likely to have a problem in the head rather than in the blood vessels, and a man who has none may need a physical check. That is the logic behind the overnight tests urologists sometimes use.

What changes with age

In a careful study of 40 healthy men aged 23 to 73, each watched over three nights in a sleep lab, night erections became fewer and shorter with every decade, and the drop could not be blamed on worse sleep. How much the cock swelled during each episode stayed the same, but most of the men over 60 no longer reached a full erection in their sleep, even though they and their partners said they were having sex regularly.

That last detail is the comforting one. A fading morning erection is a normal part of getting older, and it does not mean the daytime version has retired. The growers in the clinic study were younger, too, which hints that some of the dramatic soft-to-hard change also mellows with age.

When to see a doctor

Erections that used to reach a 3 or 4 and now stall at 1 or 2, most of the time and for weeks rather than one bad night, are worth a visit, if only to find out whether the cause is in the body or in the head. The scale on this page is exactly what the doctor will ask about, so it helps to know where you stand. The opposite problem also exists: an erection that will not go down, especially a painful one, is an emergency, not an achievement.

Everything else, the softer moments, the evenings that never get past a 2, the morning without wood, belongs to the ordinary range. The Going again chapter picks up the story after the finish line.