Cambridge will find it easier and cheaper to borrow money, since the Standard and Poor's Corporation bond rating service upped the city's credit rating from BBB + to A -, city officials said yesterday.

The improved status shows that the city is a safer debtor and could save about $160,000 in interest during its next bond sale, City Manager Robert W. Healy said yesterday.

In addition, the A - rating has prompted five investors to bid to sell the current issue of Cambridge bonds, Healy said. When the city last sold bonds in December 1982, only two establishments tried to market them.

In the past, Cambridge bonds have been rated as high as AA. The highest possible grade is AAA.

When Massachusetts passed the tax-cutting Proposition 21/2 in 1980, the ratings for 39 cities, including Cambridge, were suspended for two years because the cities' financial situations were considered shaky.