Date | Section of line | Broad | Mixed |
| 1 Jan 1872 | Total mileage | 844m 65c | 270m 58c |
| ? Feb 1872 | Didcot - Swindon (mixed) | 24m 73c - | 24m 73c |
| 11 Mar 1872 | Bristol - Floating Harbour1 | 0m 65c | |
| 1 May 1872 | Totnes - Ashburton3 | 9m 20c | |
| 11 May 1872 | All lines in South Wales and to Gloucester to standard gauge | 188m 4c - | 84m 22c - |
| 25 May 1872 | Swindon - Gloucester & Cheltenham + branches to standard gauge | 41m 76c - | 3m 41c - |
| 25 May 1872 | Lydney Junction - Pillowell (broad gauge abandoned) | 8m 19c - | |
| 25 May 1872 | Gloucester - Bristol to standard gauge2 | 32m 0c - | |
| 25 Nov 1872 | Abingdon branch to standard gauge | 1m 70c - | |
| 26 Nov 1872 | Didcot - Oxford to standard gauge | 0m 66c - | 11m 73c - |
| 1 Jul 1873 | Wiveliscombe - Barnstaple1 | 35m 25c | |
| 7 Aug 1873 | Bristol - New Passage Pier to standard gauge | 11m 73c - | 0m 36c |
| 10 Nov 1873 | Totnes - Totnes Quay3 | 0m 62c | |
| ? Jun 1874 | Swindon - Chippenham mixed | 18m 68c - | 18m 68c |
| ? Apr 1874 | Bristol - Bathampton mixed | 12m 75c - | 12m 75c |
| 20 Jun 1874 | Thingley Junction - Weymouth + branches to standard gauge | 131m 39c - | 12m 16c - |
| 26 Jun 1874 | Holt Junction - Hungerford to standard gauge | 32m 49c - | |
| 1 Jul 1874 | Savernake - Marlborough to standard gauge | 5m 49c - | |
| 1 Jul 1874 | Hungerford - Reading to standard gauge | 23m 52c - | |
| 1 Jul 1874 | Newton - Aller Junction (for Torquay branch)3 | 1m 5c | |
| 16 Jul 1874 | Watchet - Minehead1 | 8m 12c | |
| 14 Aug 1874 | Chippenham - Calne to standard gauge | 5m 24c - | |
| 16 Mar 1875 | Thingley Junction - Bathampton (mixed) | 8m 38c - | 8m 38c |
| ? May 1875 | Durston - Taunton (mixed)1 | 5m 63c - | 5m 63c |
| 1 Jun 1875 | Bristol - Highbridge (mixed)1 | 27m 6c - | 27m 6c |
| 4 Jun 1875 | Southall - Brentford to standard gauge | 3m 77c - | |
| 1 Jul 1875 | Weston Junction - Weston-super-Mare (mixed)1 | 1m 38c - | 1m 38c |
| ? Nov 1875 | West London Railway junctions to standard gauge | 4m 26c - | |
| 15 Nov 1875 | Yatton - Wells to standard gauge1 | 17m 42c | |
| 1 Mar 1876 | Taunton - Exeter (mixed) | 29m 47c- | 29m 47c |
| 24 Mar 1876 | Twyford - Henley to standard gauge | 4m 47c - | |
| 17 May 1876 | Lydford - Plymouth (mixed) | 22m 33c - | 22m 33c |
| 17 May 1876 | Devonport Jctn - Keyham Jctn (mixed + extended) | 2m 17c - | 2m 41c |
| ? Jun 1876 | Bristol Harbour Extension | 0m 39c | |
| 31 Dec 1876 | Total mileage | 273m 42c | 274m 25c |
| Metric conversion: 80 chains = 1 mile; 5 miles = 8 kilometres | |||
| Note 1: | Bristol & Exeter Railway | ||
| Note 2: | Midland Railway (formerly Bristol & Gloucester Railway) | ||
| Note 3: | South Devon Railway | ||
Locomotive Class | No. (+/-) | Total | |
| 1 Jan 1872 | Total locomotives | 432 | |
| Fire Fly 2-2-2 | - 8 | 8 | |
| Sun 2-2-2 | - 5 | 1 | |
| Leo 2-4-0 | - 3 | 0 | |
| Iron Duke 4-2-2 | -14 | 12 | |
| Premier 0-6-0 | - 1 | 0 | |
| Pyracmon 0-6-0 | - 5 | 0 | |
| Bogie 4-4-0T | -12 | 1 | |
| Waverley 4-4-0 | -10 | 0 | |
| Victoria 2-4-0 | - 1 | 17 | |
| Ceasar 0-6-0 | - 5 | 2 | |
| Banking 0-6-0T | 3 | ||
| Standard Goods 0-6-0 | -32 | 67 | |
| Metropolitan 2-4-0T | -19 | 2 | |
| Hawthorn 2-4-0 | - 4 | 22 | |
| Swindon 0-6-0 | 14 | ||
| Sir Watkin 0-6-0T | 6 | ||
| Iron Duke Renewals (Rover) 4-2-2 | + 6 | 9 | |
| Convertible 0-6-0 | +30 | 30 | |
| B&ER 4-2-2 | - 5 | 8 | |
| B&ER 0-6-0 | - 2 | 16 | |
| B&ER 4-2-4T | 6 | ||
| B&ER 4-4-0T | + 6 | 26 | |
| B&ER 2-2-2T | - 5 | 2 | |
| B&ER 0-6-0T | + 2 | 5 | |
| B&ER 2-4-0 | + 6 | 14 | |
| B&ER 0-4-0T | + 2 | 2 | |
| VofNR 4-4-0T | - 7 | 2 | |
| VofNR 0-6-0T | - 5 | 5 | |
| SDR 4-4-0T | +10 | 45 | |
| SDR 0-6-0T | 17 | ||
| SDR 0-4-0T | + 8 | 9 | |
| SDR 2-4-0T | 2 | ||
| CCR 4-4-0T | 4 | ||
| TBR 0-4-0T | 1 | ||
| Unclassified engines | - 1 | 0 | |
| 31 Dec 1876 | Total locomotives | -74 | 358 |
| 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 | ||