Ten miles pulling the trailer should go in the log book as 20 miles, right? That’s my rule of thumb. Calories burned per mile? Double that, too!
The truth ain’t that far off, the math is fairly simple, the variables, however, make this a matter best left for scientists and philosophers.
Calories Burned While Cycling
Speed and weight determine calories burned:
- 15 mph = 0.049 calories per pound per minute
- 25 mph = 0.139 calories per pound per minute
Calories burned per pound per mile ridden is not a linear function — going from 15 miles an hour to 30 miles an hour doesn’t double your calories burned. Drag is proportional to the square of speed. Thus overcoming drag at higher speeds results in far more calories being burned. Just trust me when I say Aerodynamic drag is complicated and let’s do some examples
Cyclist at 130 Pounds
- 15 mph = 0.049 calories * 130 pounds = 6.37 calories per minute
- 15 mph = 25 calories per mile
- 25 mph = 0.139 calories * 130 pounds = 18.07 calories per minute
- 25 mph = 43 calories per mile
Cyclist at 180 Pounds
- 15 mph = 0.049 calories * 180 pounds = 8.82 calories per minute
- 15 mph = 35 calories per mile
- 25 mph = 0.139 calories * 180 pounds = 25.02 calories per minute
- 25 mph = 60 calories per mile
Cyclist at 220 Pounds (ie: me)
- 15 mph = 0.049 calories * 220 pounds = 10.78 calories per minute
- 15 mph = 43 calories per mile
- 25 mph = 0.139 calories * 220 pounds = 30.58 calories per minute
- 25 mph = 73 calories per mile
Calories Burned While Pulling a Trailer
My nearly four-year-old son clocks in at 45 pounds. His trailer weighs about 30 pounds. He has another ten pounds of toys, snacks and drinks. That means I’m hauling around 85 more pounds.
Since I’m positive I’m not going 25 miles an hour while pulling the bike trailer, let’s isolate just that 85 pound load at 15 miles an hour…
- 15 mph = 0.049 calories * 85 pounds = 4.165 more calories per minute
- 15 mph = 17 more calories per mile
That means it takes 40% more energy to pull the trailer than to just drive myself around, all else being equal.
As a 220-pound cyclist, it costs me 43 calories per mile to ride. Toss the trailer on there and I’m burning roughly (very roughly) 60 calories per mile.
For a lighter biker, the trailer is a larger percentage of the total weight involved in the trip. As such, the lighter the rider, the more meaningful the increase in calories burned while pulling the trailer.
Why This Calculation Isn’t Right
The above calculations don’t consider the shape of the trailer. All they are doing is making the cyclist fatter. I’m sure even a fat biker is more aerodynamic than a box-like trailer. These calculations also don’t consider that there are two more tires in the mix affecting both friction on the road and the tires’ rotational momentum. Add in a head wind or tail wind and you’d have to recalculate. These numbers also only apply to flat rides. Add in some hills and you’re on your own.
My Bike Gets 517 Miles Per Gallon
A gallon of gas has 31,000 calories of energy, give or take.
To figure out how many miles per gallon you get on your bike, first figure out how many calories you are burning on your bike. Then, take that number and divide it into 31,000.
As I noted above, I burn 60 calories a mile when pulling the trailer. 31,000 divided by 60 is about 517 miles per gallon. Keep that in mind the next time that coworker talks about his Toyota Prius.
Just Double Up and Call It a Day
At the end of the day, I just call it double. Pulling a trailer is simply double the effort of not pulling a trailer. It takes twice as long to get out the door with a kid and trailer. It takes twice as long to get anywhere. I have to pay double the attention to traffic and the road itself. There are twice as many potty stops.
Fortunately, riding with the kid in the trailer makes me feel twice as good so it all averages out in the end.