The northern terminus of NH 118 is at New Hampshire Route 112 (the Lost River Road) in Woodstock.

The road runs southward through the towns of Warren, Wentworth, Rumney, and Dorchester.

The southern terminus of NH 118 is at U.S. Route 4 in Canaan.

From Canaan to Wentworth, the highway is named Dorchester Road.

The section from Warren to the Lost River is known as the Sawyer Highway.