The B181 is a fairly long B-road forming a loop off the A414.
It starts at a roundabout on the A414 and A1170 (former A10) and heads east along the pre-bypass A414 through Stanstead Abbotts, after which it meets the A414 again at a GSJ with east-facing sliproads. This marks the original western end of the B181.
The B181 then crosses the West Anglia Main Line at a level crossing and then the River Stort immediately afterwards to enter the village of Roydon. At the far end of the High Street traffic has to give way and the B181 turns right at the T-junction. The road now skirts Harlow New Town (at a distance; the B1133 provides access) before going through Epping Green and Epping Upland and then meeting the B182 at a junction with an attractive fingerpost. Eventually the road enters Epping itself.
The original eastern end of the B181 was at the T-junction in Epping on the original A11 (now B1393. However, with the building of the M11 and the downgrading of many roads in the area the B181 continues. It multiplexes north along the B1393 for a few hundred yards before turning right along what used to be the A122. It crosses an offshoot of Epping Forest before going under the M11 and going through North Weald Bassett. The B181 ends at the other end of town, once again on the A414.