Date | Section of line | Broad | Mixed |
| 1 Jan 1877 | Total mileage | 273m 42c | 274m 25c |
| 1 Jun 1877 | St. Erth - St. Ives | 4m 22c | |
| 3 Oct 1877 | Hayles Wharf branch (to standard gauge) | 0m 65c - | |
| 1 Feb 1878 | Plymouth Laira Jctn - Friary Jctn (mixed) | 0m 59c- | 0m 59c |
| 18 Jun 1878 | Plymouth North Rd Jctn - Millbay (mixed) | 0m 69c - | 0m 69c |
| 10 Aug 1878 | Faringdon - Uffington to standard gauge | 3m 49c - | |
| 30 Jun 1879 | Durston - Yeovil to standard gauge | 20m 35c - | |
| 30 Jun 1879 | Weston Jctn - Weston-super-Mare to standard gauge | 1m 38c - | |
| 27 Oct 1879 | Yatton - Clevedon to standard gauge | 3m 45c - | |
| 6 Nov 1879 | Plymouth Sutton Harbour North Quay branch | 0m 32c | |
| 31 Dec 1879 | Lostwithiel - Fowey (closed) | 4m 60c - | |
| 24 Jan 1880 | Portishead branch to standard gauge | 9m 49c - | |
| 14 May 1881 | Norton Fitzwarren - Barnstaple to standard gauge | 42m 50c - | |
| 31 Dec 1881 | Total mileage | 212m 35c | 254m 55c |
| Metric conversion: 80 chains = 1 mile; 5 miles = 8 kilometres | |||
Locomotive Class | No. (+/-) | Total | |
| 1 Jan 1877 | Total locomotives | 358 | |
| Fire Fly 2-2-2 | - 8 | 0 | |
| Sun 2-2-2 | - 1 | 0 | |
| Iron Duke 4-2-2 | - 9 | 3 | |
| Bogie 4-4-0T | - 1 | 0 | |
| Victoria 2-4-0 | -17 | 0 | |
| Ceasar 0-6-0 | - 2 | 0 | |
| Banking 0-6-0T | - 1 | 2 | |
| Standard Goods 0-6-0 | -62 | 5 | |
| Metropolitan 2-4-0T | - 2 | 0 | |
| Hawthorn 2-4-0 | 22 | ||
| Swindon 0-6-0 | 14 | ||
| Sir Watkin 0-6-0T | 6 | ||
| Iron Duke Renewals (Rover) 4-2-2 | +12 | 21 | |
| Convertible 0-6-0 | + 5 | 35 | |
| B&ER 4-2-2 | - 2 | 6 | |
| B&ER 0-6-0 | - 2 | 14 | |
| B&ER 4-2-4T | - 2 | 4 | |
| B&ER 4-4-0T | - 6 | 20 | |
| B&ER 2-2-2T | - 2 | 0 | |
| B&ER 0-6-0T | - 1 | 4 | |
| B&ER 2-4-0 | 14 | ||
| B&ER 0-4-0T | - 2 | 0 | |
| VofNR 4-4-0T | - 2 | 0 | |
| VofNR 0-6-0T | - 2 | 3 | |
| SDR 4-4-0T | - 9 | 36 | |
| SDR 0-6-0T | - 1 | 16 | |
| SDR 0-4-0T | 9 | ||
| SDR 2-4-0T | 2 | ||
| CCR 4-4-0T | 4 | ||
| TBR 0-4-0T | 1 | ||
| 31 Dec 1881 | Total locomotives | -117 | 241 |
| 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 | ||