douglas burke wrote:
https://www.serpentine.org.uk/pages/advice_frank52.htmlDouble your best 400 time plus 3.5-7.5 seconds per lap, For Mclaughlin (50.07) it equals 1:47.14 -1:55.14
see chart at bottom.
Everyone consistently misquotes the late Horwill on this matter. He knew the conversion matters immensely on the type of athlete.
From the same article:
"Those possessing superior speed at 400m, in the range from 44 to 46 seconds who race mainly 400 and 800 metres only. These are invariably tall, well-built athletes, who are heavier than the longer middle-distance men, their weekly mileage is around 45 kilometres, mostly high quality work. They have a poor conversion ratio per 400m in the two-lap race compared to their best 400m time. This figure is usually eight seconds, eg best 400m = 45 secs +8 = 53 secs x 2 = 1 min 46 secs. Juantorena and Courtney, both Olympic gold medallists in the 800m fall into this category."
For a pure 400m runner just attempting the 800m, she can't hope for better than at least 12s.