First and second-class stamps are being increased by 3p to 39p and 30p from April.
It will be the second set of rises in 12 months after similar increases last April.
First class stamps then went up by 2p to the current 36p and second class by 3p to the present 27p.
Business customers will see average price rises of 4.2%.
But firms using franking machines and pre-paid accounts will face slightly lower increases.
The Royal Mail said that even after the rises, UK stamp prices would remain among the lowest in Europe.
Stamped mail will still be a loss-maker after the new prices come into effect, the company added.
Luisa Fulci, Royal Mail's director of marketing services, said: "Consumers are still receiving excellent value for money - most countries in Europe charge more to deliver less."
The Royal Mail said the rise in emailing and texting is accelerating the decline in the postal market.
The recent Hooper report predicted mail volumes could fall by between 5% and 7% a year.
Around five million fewer letters are being delivered every day compared with two years ago.
