Prices at different toll points and toll ring areas can be found on the relevant toll road company’s website:
Prices Fjellinjen (Oslo)
Prices Ferde (South- and Western Norway)
Prices Vegfinans (Eastern Norway)
Prices Vegamot (Trøndelag and Møre og Romsdal)
Prices Bompengeselskap Nord (Northern Norway)
Prices The Great Belt Bridge
Prices The Øresund connection
You can also calculate prices via the unofficial website bompengekalkulator.no, but be aware that prices may be incorrect.