dissenting.
From reading the Court’s opinion in this case, one would surely conclude that the Southern Ohio Correctional Facility (SOCF) is a safe, spacious prison that happens to include many two-inmate cells because the State has determined that that is the best way to run the prison. But the facility *370described by the majority is not the one involved in this case. SOCF is overcrowded, unhealthful, and dangerous. None of those conditions results from a considered policy judgment on the part of the State. Until the Court’s opinion today, absolutely no one — certainly not the “state legislatures” or “prison officials” to whom the majority suggests, see ante, at 352, that we defer in analyzing constitutional questions — had suggested that forcing long-term inmates to share tiny cells designed to hold only one individual might be a good thing. On the contrary, as the District Court noted, “everybody” is in agreement that double celling is undesirable.1 No one argued at trial and no one has contended here that double celling was a legislative policy judgment. No one has asserted that prison officials imposed it as a disciplinary or a security matter. And no one has claimed that the practice has anything whatsoever to do with “punish [ing] justly,” “deter [ring] future crime,” or “return [ing] imprisoned persons to society with an improved chance of being useful, law-abiding citizens.” See ante, at 352. The evidence and the District Court’s findings clearly demonstrate that the only reason double celling was imposed on inmates at SOCF was that more individuals were sent there than the prison was ever designed to hold.2
I do not dispute that the state legislature indeed made policy judgments when it built SOCF. It decided that Ohio needed a maximum-security prison that would house some 1,600 inmates. In keeping with prevailing expert opinion, the legislature made the further judgments that each inmate would have his own cell and that each cell would have approximately 63 square feet of floor space. But because of prison overcrowding, hundreds of the cells are shared, or “doubled,” which is hardly what the legislature intended.
*371In a doubled cell, each inmate has only some 30-35 square feet of floor space.3 Most of the windows in the Supreme Court building are larger than that. The conclusion of every expert who testified at trial and of every serious study of which I am aware is that a long-term inmate must have to himself, at the very least, 50 square feet of floor space — an area smaller than that occupied by a good-sized automobile— in order to avoid serious mental, emotional, and physical deterioration.4 The District Court found that as a fact. 434 *372F. Supp. 1007, 1020-1021 (SD Ohio 1977). Even petitioners, in their brief in this Court, concede that double celling as practiced at SOCF is “less than desirable.” Brief for Petitioners 17.
The Eighth Amendment “embodies ‘broad and idealistic concepts of dignity, civilized standards, humanity, and decency,’ ” against which conditions of confinement must be judged. Estelle v. Gamble, 429 U. S. 97, 102 (1976), quoting Jackson v. Bishop, 404 F. 2d 571, 579 (CA8 1968). Thus the State cannot impose punishment that violates “the evolving standards of decency that mark the progress of a maturing society.” Trop v. Dulles, 356 U. S. 86, 101 (1958) (plurality opinion). For me, the legislative judgment and the consistent conclusions by those who have studied the problem provide considerable evidence that those standards condemn imprisonment in conditions so crowded that serious harm will result.. The record amply demonstrates that those conditions are present here. It is surely not disputed that SOCF is severely overcrowded. The prison is operating at 38% above its design capacity.5 It is also significant that *373some two-thirds of the inmates at SOCF are serving lengthy or life sentences, for, as we have said elsewhere, “the length of confinement cannot be ignored in deciding whether the confinement meets constitutional standards.” Hutto v. Finney, 437 U. S. 678, 686 (1978). Nor is double celling a short-term response to a temporary problem. The trial court found, and it is not contested, that double celling, if not enjoined, will continue for the foreseeable future. The trial court also found that most of the double-celled inmates spend most of their time in their cells.6
*374It is simply not true, as the majority asserts, that “there is no evidence that double celling under these circumstances either inflicts unnecessary or wanton pain or is grossly disproportionate to the severity of crimes warranting imprisonment.” Ante, at 348. The District Court concluded from the record before it that long exposure to these conditions will “necessarily” involve “excess limitation of general movement as well as physical and mental injury . . . .” 434 F. Supp., at 1020 (emphasis added).7 And of course, of all the judges who have been involved in this case, the trial judge is the only one who has actually visited the prison. That is simply an additional reason to give in this case the *375deference we have always accorded to the careful conclusions of the finder of fact. There is not a shred of evidence to suggest that anyone who has given the matter serious thought has ever approved, as the majority does today, conditions of confinement such as those present at SOCF. I see no reason to set aside the concurrent conclusions of two courts that the overcrowding and double celling , here in issue are sufficiently severe that they will, if left unchecked, cause deterioration in respondents’ mental and physical health. These conditions in my view go well beyond contemporary standards of decency and therefore violate the Eighth and Fourteenth Amendments. I would affirm the judgment of the Court of Appeals.
If the majority did no more than state its disagreement with the courts below over the proper reading of the record, I would end my opinion here. But the Court goes further, adding some unfortunate dicta that may be read as a warning to federal courts against interference with a State’s operation of its prisons. If taken too literally, the majority’s admonitions might eviscerate the federal courts’ traditional role of preventing a State from imposing cruel and unusual punishment through its conditions of confinement.
The majority concedes that federal courts “certainly have a responsibility to scrutinize claims of cruel and unusual confinement,” ante, at 352, but adds an apparent caveat:
“In discharging this oversight responsibility, however, courts cannot assume that state legislatures and prison officials are insensitive to the requirements of the Constitution or to the perplexing sociological problems of how best to achieve the goals of the penal function in the criminal justice system: to punish justly, to deter future crime, and to return imprisoned persons to society with an improved chance of being useful, law-abiding citizens.” Ibid.
As I suggested at the outset, none of this has anything to *376do with this case, because no one contends that the State had those goals in mind when it permitted SOCF to become overcrowded. This dictum, moreover, takes far too limited a view of the proper role of a federal court in an Eighth Amendment proceeding and, I add with some regret, far too sanguine a view of the motivations of state legislators and prison officials. Too often, state governments truly are “insensitive to the requirements of the Eighth Amendment,” as is evidenced by the repeated need for federal intervention to protect the rights of inmates. See, e. g., Hutto v. Finney, 437 U. S. 678 (1978) (lengthy periods of punitive isolation); Estelle v. Gamble, 429 U. S. 97 (1976) (failure to treat inmate’s medical needs); Battle v. Anderson, 564 F. 2d 388 (CA10 1977) (severe overcrowding); Gates v. Collier, 501 F. 2d 1291 (CA5 1974) (overcrowding and poor housing conditions); Holt v. Sarver, 442 F. 2d 304 (CA8 1971) (unsafe conditions and inmate abuse); Pugh v. Locke, 406 F. Supp. 318 (MD Ala. 1976) (constant fear of violence and physical harm), aff’d, 559 F. 2d 283 (CA5 1977), rev’d in part on other grounds, 438 U. S. 781 (1978) (per curiam). See also ante, at 353-361 (Brennan, J., concurring in judgment).8
*377A society must punish those who transgress its rules. When the offense is severe, the punishment should be of proportionate severity. But the punishment must always be administered within the limitations set down by the Constitution. With the rising crime rates of recent years, there has been an alarming tendency toward a simplistic penological philosophy that if we lock the prison doors and throw away the keys, our streets will somehow be safe. In the current climate, it is unrealistic to expect legislators to care whether the prisons are overcrowded or harmful to inmate health. It is at that point — when conditions are deplorable and the political process offers no redress — that the federal courts are required by the Constitution to play a role. I believe that this vital duty was properly discharged by the District Court and the Court of Appeals in this case. The majority today takes a step toward abandoning that role altogether. I dissent.
“The experts were all in agreement — as is everybody — that single celling is desirable.” 434 F. Supp. 1007, 1016 (SD Ohio 1977).
See id., at 1010-1011.
The bed alone, which is bunk-style in the doubled cells, takes up approximately 20 square feet. Thus the actual amount of floor space per inmate, without making allowance for any other furniture in the room, is some 20-24 square feet, an area about the size of a typical door.
See, e. g., American Public Health Assn., Standard for Health Services in Correctional Institutions 62 (1976) (“a minimum of 60 sq. ft.”); Commission on Accreditation for Corrections, Manual of Standards for Adult Correctional Institutions 27 (1977) (“a floor area of at least 60 square feet”; “[i]n no case should the present use of the facility exceed designed use standards”); 3 National Institute of Justice, American Prisons and Jails 85, n. 6 (1980) (“80 square feet of floor space in long-term institutions”); National Sheriffs’ Assn., A Handbook on Jail Architecture 63 (1975) (“[s]ingle occupancy detention rooms should average 70 to 80 square feet in area”); U. S. Dept, of Justice, Federal Standards for Prisons and Jails 17 (1980) (“at least 60 square feet of floor space”); National Council on Crime and Delinquency, Model Act for the Protection of Rights of Prisoners, 18 Crime & Delinquency 4, 10 (1972) (“not less than fifty square feet of floor space in any confined sleeping area”). Most of these studies recommend even more space for inmates who must spend more than 10 hours per day in their cells. One expert witness, a former warden of Rikers Island, testified from his experience that the double celling, if continued over “an awful long stretch of time,” could be expected to lead to “assault behavior” and “homosexual occurrences.” Tr. 48. He added that “skid row bums” in Bowery flophouses tend to live in healthier surroundings than do double-celled inmates. Id., at 55. As will become apparent, the majority and I disagree ove,r the weight to be given these studies and the expert testimony. But I emphasize that the majority has not pointed to a single witness or study refuting or even contradicting the conclusion of panel after panel of experts that an inmate needs as an absolute minimum 50 square feet of floor space to himself to avoid deterioration of his health.
In my dissenting opinion in Bell v. Wolfish, 441 U. S. 520, 572, n. 12 (1979), I pointed out that the majority ignored “the rated capacity of the institution” in determining whether the challenged overcrowding was unconstitutional. In its opinion today, the Court at least mentions that SOCF is operating at 38% above its rated capacity, but it dismisses that rating as “[p]erhaps” reflecting “an aspiration toward an ideal environment for long-term confinement.” Ante, at 349. “The question before us,” the majority adds, “is not whether the designer of SOCF guessed incorrectly about future prison population, but whether the actual conditions of confinement at SOCF are cruel and unusual.” Ante, at 350-351, n. 15. Rated capacity, the majority argues, is irrelevant because of the numerous factors that influence prison population. Actually, it is the factors that influence prison population that are irrelevant. By definition, rated capacity represents “the number of inmates that a confinement unit, facility, or entire correctional agency can hold.” 3 National Institute of Justice, American Prisons and Jails 41-42 (1980). If prison population, for whatever reason, exceeds rated capacity, then the prison must accommodate more people than it is designed to hold — in short, it is over*373crowded. And the greater the proportion by which prison population exceeds rated capacity, the more severe the overcrowding. I certainly do not suggest that rated capacity is the only factor to be considered in determining whether a prison is unconstitutionally overcrowded, but I fail to understand why the majority feels free to dismiss it entirely.
Although the majority suggests, ante, at 344, n. 8, that this finding lacks a clear basis, the trial court also found as a fact that most inmates are out of their cells only 10 hours each day. 434 F. Supp., at 1013. This leaves 14 hours per day inside the cell. The trial court also found that a “substantial number” of inmates are out of their cells for no more than four to six hours per week. Id,., at 1021.
The majority assumes, ante, at 350, n. 15, that the trial court’s finding that most inmates are out of their cells only 10 hours each day is “flatly inconsistent” with its finding that regulations permit most inmates to be out of their cells up to 14 hours each day. The majority goes on to reject the first finding in favor of the second. A more reasonable course would be to read these two findings in such a way as to give meaning to both. Thus I read the District Court’s opinion as finding that although most inmates are permitted to be out of their cells up to 14 hours each day, conditions in the prison are such that many choose not to do so.
The majority also attaches importance to the fact that the inmates who are locked in their cells for all but four to six hours a week are in a “restrictive classification.” Ibid. It is not clear to me why this matters. The inmates who are out of their cells only four to six hours each week are in three categories: “receiving,” a category in which new inmates are placed for “a couple of weeks”; “voluntarily idle,” which presumably means what it says; and “limited activity,” for those inmates who have requested, but have not received, protective custody. It is not immediately apparent why classification in any of these categories justifies *374imposition of otherwise cruel and ususual punishment. In particular, the State surely lacks authority to force an individual to choose between possibility of rape or other physical harm (the presumed reason for the request for protective custody) and unconstitutionally cramped quarters. The majority asserts, incorrectly, that some of these inmates have committed rule infractions. Ibid. In fact, inmates who commit infractions are out of their cells only two hours each week. 434 F. Supp., at 1013. Although this dissent has not addressed their particular plight, it is beyond question that if punishment is cruel and unusual, then the mere fact that an individual prisoner has committed a rule infraction does not warrant its imposition. See Hutto v. Finney, 437 U. S. 678, 685-688 (1978).
In its findings, the District Court credited expert testimony that “close quarters” would likely increase the incidence of schizophrenia and other mental disorders and that the double celling imposed in this case had led to increases in tension and in “aggressive and anti-social characteristics.” 434 F. Supp., at 1017. There is no dispute that the prison was violent even before it became overcrowded, and that it has become more so. Contrary to the contention by the majority, ante, at 349-350, n. 15, I do not assert that violence has increased due to double celling. I accept the finding of the District Court that violence has increased due to overcrowding. See 434 F. Supp., at 1018. Plainly, this case involves much more than just the constitutionality of double celling per se. Other federal courts faced with overcrowded conditions have reached similar conclusions. See, e. g., Campbell v. McGruder, 188 U. S. App. D. C. 258, 273, 580 F. 2d 521, 536 (1978); Battle v. Anderson, 564 F. 2d 388, 399-401 (CA10 1977) ; Detainees of Brooklyn House of Detention v. Malcolm, 520 F. 2d 392, 396, 399 (CA2 1975).
The majority’s treatment of the expert evidence in this case also calls for some comment. The Court asserts that expert opinions as to what is desirable in a prison “may be helpful and relevant with respect to some questions” but “ 'simply do not establish the constitutional minima; rather, they establish goals recommended by the organization in question.’ ” Ante, at 348, n. 13, quoting Bell v. Wolfish, 441 U. S., at 543-544, n. 27. That is more or less a truism, but it plainly does not advance analysis. No one would suggest that a study, no matter how competent, could ever establish a constitutional rule. But once the rule is established, it is surely the case that expert evidence can shed light on whether the rule is violated. Cf. Brown v. Board of Education, 347 U. S. 483, 494, n. 11 (1954) (using psychological studies to show harm from segregation). Thus even if it is true, as the majority asserts, that the Eighth Amendment forbids only a punishment that “either inflicts unnecessary or wanton pain or is grossly disproportionate to the severity of crimes warranting imprisonment,” ante, at 348, surely a court faced with a claim of unconstitutionality would want to know whether anyone had in fact studied the *377effect of the punishment in issue. Deciding whether that effect was of unconstitutional proportions, and, indeed, whether the study was competently done, would naturally remain the court’s function. Here, the trial court deemed the expert opinion presented to it worthy of considerable weight in its assessment of the conditions at SOCF. The majority, however, casts it aside without even a token evaluation of the methodology, content, or results of any of the studies on which the District Court relied. If expert opinion is of as little value as the majority implies, then even plaintiffs with meritorious claims that their conditions of confinement violate the Eighth Amendment will have tremendous difficulty in proving their cases.