The Metro board formally proposed yesterday a vastly revised bus and subway fare schedule that will increase rates for suburban rush-hour commuters and the Metro lunch bunch but leave fares as they are for most District of Columbia residents.

Metro also is proposing a two-week transit pass that will give its buyer unlimited bus rides and $5 worth of subway trips for $10. Although available to everyone, the $10 pass will be most useful in Washington. More expensive passes are proposed for all of suburban Maryland and parts of northern Virginia.

The fare schedule and transit pass proposals will become effective July 1 if they are formally adopted by the board after public hearings, which are scheduled throughout the metropolitan area in late April.

Adoption of the fare package will probably make possible the extension of subway service to Saturdays and weeknights, beginning in September, according to Metro board members. Extended service is part of the pending Metro budget for the next fiscal year, but the budget presumes a fare increase of about 7 percent to finance extra service and inflation-fed costs. Without the fare increase, board members have been unwilling to approve the budget.

Under the proposal, rush-hour round-trip fares for most suburbanites using both bus and subway to get to work will increase by 30 cents a day. Rush hour is defined by Metro as 6 a.m. to 9:30 a.m. and 3 p.m. to 6:30 p.m. weekdays.

Rush-hour subway-only fares for most District of Columbia residents will remain the same - 40 cents - and there will be no change in the District of Columbia bus fare, which is 50 cents in the rush hour and 40 cents the rest of the time. The cost of keeping the fares down in Washington will be borne by the D.C. government through increased subsidies to Metro.

The proposed subway fare has four specific features:

The present rush-hour charge of 40 cents for three miles will remain for all subway trips except those that cross the Potomac River. After the first three rush-hour miles, riders will pay 8.5 cents for each additional mile, rounded to the nearest nickel. That is a 1-cent increase per mile over today's fare. The automated fare-collecting equipment Metro uses computes the cost of each trip and deducts it from a magnetically encoded Farecard the rider buys.

All riders who take the subway across the Potomac River during rush hour will pay a minimum of 45 cents, plus the mileage charge of 8.5 ce, per mile after three miles.

During nonrush hour periods, the cost of all subway trips, regardless of distance, will be 50 cents. That includes a trip from Silver Spring to National Airport, which would cost $1.15 during rush hour, as well as one from the adjacent Gallery Place and Judiciary Square stations, which would cost 40 cents during rush hours.

When the Blue Line is extended from Stadium-Armory to New Carrollton late this year, special reduced rush-hour fares will be available for all people entering and leaving the Deanwood and Minnesota Avenue stations. Those stations, both in the District of Columbia and both east of the Anacostia River, are in predominantly low-income areas and the D.C. government will reimburse the Metro treasury for the difference between the fares collected and the fares that would normally be collected.

Under the normal rush-hour formula, the trip from Deanwood to Metro Center would cost 65 cents: the District of Columbia probably will reduce it to 55 cents. The trip from Minnesota Avenue to Metro Center would cost 60 cents, but probably will be reduced to 50 cents.

The subway formula, while complicated, is much simpler than a series of formulas that were under discussion as late as Tuesday night by Metro board members. The central issue that had to be solved was the insistence by the District of Columbia that fares not be increased for short trips - those most likely to be taken by Washington residents.

Suburban jurisdictions, especially those in Virginia, were equally concerned about financing as much of the Metro operation as possible from fares, not from property-tax supported subsidies.

The formula approved yesterday was worked out Wednesday in a series of meetings and phone calls involving primarily Metro board chairman Joseph S. Wholey, a member of the Arlington County Board, and D.C. transportation director Douglas Schnider, Mayor Walter Washington's representative to the Metro board. Weeks of tough, sometimes vitriolic negotiations led to the final package that sailed through an early-morning Metro Board committee meeting yesterday in 24 minutes. It was subsequently tentatively approved by the full board with little debate.

All sides, suburban and inner city, were anxious to begin extended weekday and Saturday service on the subway, which now runs only on weekdays from 6 a.m. to 8 p.m. If no fare increase is finally approved, that extra service will certainly be the first casualty.

Assuming the fare package survives public hearings and Metro's revised new budget is promptly adopted, subway service will be extended to 11 p.m. weeknights and run for 14 hours on Saturdays beginning in September.

The fare package, including the transit passes, will represent about a $4 million drop in revenues from those projected for Metro's $195 million operating budget for fiscal 1979, beginning July 1. The operating deficit is projected at about $98 million, most of which will be paid by state and local subsidies.

Most of the $4 million revenue loss will be reimbursed to the Metro treasury by the District of Columbia government, because it is for Washingtonians that the fares will remain at essentially their present levels.

D.C. resident absorbed a big fare increase in July, and another increase in this D.C. election year "is not politically possible," as City Council and Metro board member Jerry Moore said recently.

Moore praised the fare package yesterday as a good compromise. "I think we finally came out with that Saturday and weeknight service which we all wanted," Moore said.

The 50-cent flat fare for all subway trips during mid day does represent an increase over the 40-cent rush-hour for short trips. But Schneider said it had long-term benefits for many D.C. residents who work odd hours, and could take advantage of the subway for trips to places like Silver Spring and Rosslyn without having to pay high fares. The 50-cent flat fare will also be popular on Saturdays for family travel throughout the region, Schneider said.

There are also several changes proposed in the suburban bus fares:

The nonrush hour fare in Virginia will increase from 40 cents to 50 cents.

The bus zone charge between Virginia Zone 1 and Zone 2 will also be increased 10 cents. The net result is that an all-bus trip from Springfield (in Zone 2) to Washington now will cost $1.30 instead of $1.10.

Maryland residents will have to start paying the 20-cent per zone charge when they transfer from rail to bus within the District of Columbia. No more free rides from Dupont Circle to Rockville after paying only a 40-cent subway fare at night.

Maryland Zones 2, 3 and 4 will be combined into one, huge Zone 2, thus reducing the number of zone charges for the long trip.

Express buses from Montgomery Mall and the Korvettes parking lot on Rockville Pike will cost 25 cents more each way.

All public hearings on fares and transit passes will begin at 7:30 p.m. The dates and locations are as follows:

Monday, April 17, Alexandria City Council chambers, 125 North Royal St.

Tuesday, April 18, Benjamin Stoddert Junior High School, 2501 Olson St., Marlow Heights.

Wednesday, April 19, County Office Building, 100 Maryland Ave., Rockville.

Monday, April 24, Swanson Junior High School, 5800 North Washington Blvd., Arlington.

Tuesday, April 25, Maryland-National Capital Park and Planning Commission, 8787 Georgia Ave., Silver Spring.

Wednesday, April 26, Lincoln Junior High School, 16th and Irving streets NW Washington.

Thursday, April 27, Groveton High School, 6500 Quander La., Alexandria.

Monday, May 1, Ballou Senior High School, 4th and Trenton streets SE, Washington.

Tuesday, May 2, Woodson Senior High School, 55th and Eads streets NE, Washington.

Wednesday, May 3, George Mason Junior-Senior High School, Leesburg Pike and Haycock Road, Falls Church.

Thursday, May 4, Center for Adult Education, University of Maryland, Adelphi Road and Campus Drive, College Park.Information on the hearing is available by calling 637-1050.