Date | Section of line | Broad | Mixed |
| 1 Jan 1882 | Total mileage | 212m 35c | 254m 55c |
| 28 Oct 1882 | Norton Fitzwarren - Minehead to standard gauge | 22m 60c- | |
| 30 Jun 1883 | Slough - Windsor to standard gauge | 3m 5c - | |
| 28 Jun 1884 | Tiverton branch to standard gauge | 4m 60c | |
| 31 Dec 1886 | Total mileage | 184m 75c | 251m 50c |
| Metric conversion: 80 chains = 1 mile; 5 miles = 8 kilometres | |||
Locomotive Class | No. (+/-) | Total | |
| 1 Jan 1882 | Total locomotives | 241 | |
| Iron Duke 4-2-2 | - 3 | 0 | |
| Banking 0-6-0T | - 1 | 1 | |
| Standard Goods 0-6-0 | - 4 | 1 | |
| Hawthorn 2-4-0 | 22 | ||
| Swindon 0-6-0 | 14 | ||
| Sir Watkin 0-6-0T | 6 | ||
| Iron Duke Renewals (Rover) 4-2-2 | 21 | ||
| Convertible 0-6-0 | +26 | 61 | |
| Convertible 2-4-0T | +10 | 10 | |
| B&ER 4-2-2 | - 2 | 4 | |
| B&ER 0-6-0 | - 4 | 10 | |
| B&ER 4-2-4T | - 2 | 2 | |
| B&ER 4-4-0T | - 7 | 13 | |
| B&ER 0-6-0T | - 2 | 2 | |
| B&ER 2-4-0 | - 4 | 10 | |
| VofNR 0-6-0T | - 3 | 0 | |
| SDR 4-4-0T | -27 | 9 | |
| SDR 0-6-0T | 16 | ||
| SDR 0-4-0T | - 1 | 8 | |
| SDR 2-4-0T | 2 | ||
| CCR 4-4-0T | 4 | ||
| TBR 0-4-0T | 1 | ||
| 31 Dec 1886 | Total locomotives | -24 | 217 |
| Key: | B&ER - Bristol & Exeter Railway (merged with GWR Jan 1876) VofNR - Vale of Neath Railway (merged with GWR Dec 1866) SDR - South Devon Railway (merged with GWR Feb 1876) CCR - Carmathen & Cardigan Railway (broad gauge engines sold to SDR 1872) TBR - Torbay & Brixham Railway (merged with GWR Jan 1883) | ||