In Ohio last Monday, President Reagan casually said "maybe . . . the normal unemployment rate . . . instead of being that 4 percent . . . we used to talk about . . . might be 6 or 6 1/2 percent."

The inference was that if unemployment hit 10 percent, as it did in September, the president could not be blamed for all 10.1 percentage points, just the last 3.5 or 4. Or, to put it another way, 10 percent is not as bad as it seems.

All presidents try to mitigate bad economic news, but this time a genuine debate is going on.

For some years, conservatives have been arguing that unemployment implies less social pain than it used to. There are more two-earner families, they say, and more workers have unemployment insurance or are eligible for such other benefits as food stamps. In addition, they say, there is greater risk of inflation in driving down unemployment, so low unemployment also has a social cost.

Liberals say that the official rate understates unemployment, in part because it fails to account for "discouraged" workers who have dropped out of the labor force.

Is unemployment as harsh as it was 40 years ago, the last time it was in double digits in this country? Here are some facts from both sides:

Unemployment insurance payments are more generous, and atop these are other benefits to which the unemployed can turn.

The Congressional Budget Office says that for every percentage point the unemployment rate rises -- equivalent to another 1.1 million people out of work -- the federal government spends an additional $3 billion to $4 billion on unemployment benefits, $500 million on food stamps, between $100 million and $200 million on Medicaid and $100 million to $300 million on other assistance programs. That works out to almost $4,000 a year for each new addition to the jobless rolls.

The increase in two-earner households in recent years means that, even if one person in a household is out of work, another may not be. More than half of the nation's adult women are in the job market, compared to less than one-third in 1947. In the latest three months, 59 percent of the more than 10 million unemployed Americans lived in a household in which at least one other person was working.

There is also the point alluded to by Reagan that the level of "structural," or underlying, unemployment has risen in recent years so that it is no longer realistic to judge today's jobless rate by past standards.

It is impossible to push the unemployment rate below a certain "structural" rate without setting off faster inflation, analysts say. At this level there are not enough people to fill the jobs that need to be done, so wages are bid up and inflation accelerates.

While the "full employment" rate used to be put at about 4 or 4 1/2 percent, many, including Martin Feldstein, Reagan's new chairman of the Council of Economic Advisers, now say it is closer to 6 percent or 6 1/2 percent.

But even those who say it is no longer realistic to aim for a 4 percent jobless rate are unhappy with the 10.1 percent figure for September.

Unemployment has soared over the last year because of a slumping economy, not because of structural factors, analysts agree. Increasing numbers of adult breadwinners have been pushed onto the unemployment rolls this year, the newest Labor Department report shows. More than 60 percent of those without work in September were over 25. Three years earlier, when the overall unemployment rate was 5.8 percent, those over 25 accounted for only half the total.

Married people generally have a much lower unemployment rate than do singles. But today's depressed labor market affects many more married workers. Only 2.2 percent of husbands living with their wives were out of work three years ago. Now the figure is 6.4 percent.

The overall September unemployment rate, while already high, clearly understates the number of people hurt by the weak economy and poor job prospects. Last year, when the monthly unemployment rate averaged 7.6 percent, almost 20 percent of the work force was actually out of work at some point during the year. Analysts expect that figure to rise toward 25 percent this year.

In addition to those counted as unemployed, an estimated 6.6 million people were forced to work part-time last month because they could not find a full-time job, and 1.6 million would like work but gave up looking.

For those who lose jobs, the government still does not take away all the pain:

* Only 40 percent of last month's jobless were receiving unemployment insurance benefits. With more of the unemployed now out of work for a long time -- one in three had been unemployed for more than 15 weeks last month compared to one in four a year earlier -- some are reaching the end of their unemployment benefits.

* For those lucky enough to receive a benefit check, the average payment in July -- the last month for which figures are available -- was $114.60 a week, compared to average weekly earnings of $269.98.

* The drop in living standards for those who lose jobs depends greatly on where they live. In the District of Columbia, the average July unemployment check totaled $140.10. In Michigan, the most generous state, the figure was $148.21, a contrast with Alabama at $78.35 or Mississippi at $76.50.

* The pain is also concentrated. Unemployment tends to run in families and is far higher among blacks than whites and among blue-collar workers than white-collar workers. Unemployment is also bunched geographically, with a far greater proportion of the labor force out of work in old industrial and manufacturing areas.

* The unemployment rate among husbands and wives whose spouses are unemployed is about three times as high as that for those with an employed spouse.

* Teen-agers are much more likely to be unemployed than adults, with almost one in four of those who want to work now out of a job.

* Blue-collar workers have an unemployment rate of 15.6 percent, up from 10 percent a year ago. In that time, the jobless rate for professionals has crept from 2.8 percent to 3.2 percent.

* Construction and manufacturing have been much harder hit than the rest of the economy. More than one in four construction workers has been out of a job in each of the last three months. Manufacturing unemployment jumped to 13.8 percent last month.

In contrast, the jobless rate for government workers was less than 5 percent in September; for finance and service industries, 6.8 percent, and for wholesale and retail trade, 9.8 percent.