Minor increases in the costs of household services, alcohol, travel and housing contributed to the quarterly figures, with the drop in prices of food, household goods and domestic heating oil reducing the rate slightly.
The inflation level has been under the 2% mark for the last 18 months.
The separate measure for inflation without housing costs – RPI(X) – also dipped slightly, from 1.9% to 1.8%.
According to the States statistics unit, which compiles the figures, the household services category includes post and phone charges, as well as fees and subscriptions.
Increased average rents in the public and private sector also affected the rate, as did a 0.5 pence per litre increase in motor fuels.