Stationary bike calorie burn?

fiddletime

I biked 4.5 miles in 20 min this am on my new Nordic Track upright bike. It was the Central Park route with speed of 12 and resistance up to 18. My Polar H7 said I burned 81 calories. I'm new to biking and found it a moderate workout (am 5'2" and 125#). Do you think the Polar is pretty accurate to use as my calorie guide? I can't use the bike because it elevated my HR about 30% (compared bike and Polar to counting HR on my watch with my pulse). The Polar HR seemed very accurate.

Machka9

For stationary bike, no matter how hard I ride, and I usually do "commercial intervals" so I am putting some effort in, I always select: "Stationary bike, light effort (bicycling, cycling, biking)", and enter my time.

fiddletime

Ok sounds good. I'd rather underestimate burn than overestimate it.