I just realized that Sarah Jane Smith had more screen time than any Doctor aside from Tom Baker. Here’s how it breaks down, going by rough episode lengths and assuming that any episode where the character is a featured player counts for its full length:
- Tom Baker – 71 hours, 40 minutes
- Sarah Jane Smith – 61 hours
- Hartnell – 57 hours, 30 minutes
- Troughton – 55 hours
- Pertwee – 54 hours, 50 minutes
- Brigadier Lethbridge-Stewart – 50 hours, 40 minutes
- Jamie McCrimmon – 49 hours, 20 minutes
- Captain Jack Harkness – 44 hours, 37 minutes
- Tennant – 38 hours, 38 minutes
- K-9 (all models) – 38 hours, 15 minutes
- Jo Grant – 32 hours, 55 minutes
- Ian & Barbara – 32 hours, 5 minutes
- Davison – 30 hours, 48 minutes
- Tegan Jovanka – 29 hours
- Rose Tyler – 23 hours, 17 minutes
- Susan Foreman – 22 hours, 45 minutes
- Matt Smith – 21 hours, 8 minutes (through series 6)
- Amy Pond – 21 hours, 8 minutes (through series 6)
- Zoe Heriot – 20 hours, 50 minutes
- Nyssa of Traken – 20 hours, 50 minutes
- Peri Brown – 20 hours, 35 minutes
- Steven Taylor – 19 hours, 10 minutes
- Adric of Alzarius – 18:20
- McCoy – 17 hours, 30 minutes
- Colin Baker – 17 hours, 15 minutes
- Victoria Waterfield – 17 hours, 5 minutes
- Ben & Polly – 16 hours, 40 minutes
- Leela of the Sevateem – 16 hours, 40 minutes
- Romana II – 16 hours, 40 minutes
- Rory Williams – 16 hours, 38 minutes
- Vicki – 16 hours, 15 minutes
- Vislor Turlough – 14 hours, 50 minutes
- Martha Jones – 13 hours, 57 minutes
- Donna Noble – 13 hours, 35 minutes
- Ace – 12 hours, 55 minutes
- Romana I – 10 hours, 50 minutes
- Liz Shaw – 10 hours, 25 minutes
- Eccleston – 9 hours, 45 minutes
- Mickey Smith – 9 hours, 20 minutes
- Dodo Chaplet – 8 hours, 20 minutes
- Mel Bush – 8 hours, 20 minutes
- Wilfred Mott – 7 hours, 15 minutes
- Sara Kingdom – 3 hours, 45 minutes
- Kamelion – 2 hours, 30 minutes
- Katarina – 2 hours, 5 minutes
- McGann – 1 hour, 30 minutes
- Adam Mitchell – 1 hour, 30 minutes
The Brigadier is in a similar class to Sarah Jane, thanks to several seasons as a regular and decades of return appearances. Jack also holds up well, with Torchwood’s long episodes and about a season’s worth of main-series screen time. Jamie, of course, was in all of Troughton’s original episodes except the first six, and then reappeared in The Two Doctors.
Aside from the estimations and assumptions above, I am unsure how to record K-9’s SJA appearances, as he appears often but usually only for a few seconds. I’m not counting Shada, Dimensions in Time, or Richard Hurndall in The Five Doctors, or any cameo appearances. Other figures may be debatable, but I don’t really care.