The Well-Tempered Cyclist: M.P.G.

By Steve Chambers

How many m.p.g. does your bike get?
by Steve Chambers

I saw the title of this column on a sign in a bike shop. It was clearly meant to be a rhetorical question, but it got me thinking: How does cycling compare to driving, fuel efficiency-wise? We can’t just drink a gallon of gasoline and set off on our bikes to see how far we go, but by comparing the number of calories in a gallon of gasoline with the number of calories expended cycling, we can make a comparison.

A gallon of gasoline has about 31,000 calories of stored energy in it. Therefore, a car that gets 25 mpg can run a mile on about 1,240 calories (about .0008 miles per calorie).

How does this compare to a human riding a bicycle? I strapped on my heart rate monitor, which has been programmed for me, and measures my caloric expenditure based on my heart rate and other factors, and set off on a 15-mile ride, about my average commute.

At the end of my ride, according to my monitor I had burned 795 calories. I’m more like an SUV; not as fuel efficient as others. A lighter rider with a better cardiovascular system might use only 500 calories on the same ride. But for me, the math says I get about .02 miles per calorie. If I could process gasoline’s 31,000 calories per gallon into cycling energy, my mpg rating would be 585 miles per gallon. That cyclist who only expends 500 calories to ride the same 15 miles gets the equivalent of 930 mpg.

All right, you skeptics admit, it’s more efficient to ride a bike than drive, but what about cost?

Let’s compare the cost of refueling a car after a 15-mile ride versus refueling me. Assuming 25 mpg, a car burns .6 gallon of gas on a 15-mile drive. At a price of $1.75 per gallon, that’s $1.05. I expend 795 calories for that same 15-mile ride. How can I replace those calories?

Here’s where it gets interesting. While a driver has only three choices of gas, regular, mid-grade and premium, I have an almost unlimited number of choices. Considering calories only, I can eat 1.5 Big Macs (540 calories per burger); drink over five cans of coke (140 calories per can) or just over four Starbucks’ grand lattes with 2% milk (190 calories per 16 oz.). A more nutritional option for the same number of calories would be a bagel and cream cheese with a whole avocado and two boiled eggs.

Aha, you exclaim. I knew all along cycling wasn’t a less expensive means of transportation than my good old SUV. Clearly it’s going to cost less to put gas in my car than it is to feed my face if I ride.

Perhaps. But what’s the cost to society? What does that SUV emit? The average car emits 29.6 lbs. of CO2 alone per day. The average person emits 2-4 lbs of waste per day (this is just from the food we eat, just as the car’s waste is from the fuel it burns). And, you’re going to emit that waste whether you ride or not.

What of the indirect costs? What’s the carbon footprint of a car vs. a bicycle? How many gallons of water, kilowatts of electricity, pounds of natural resources such as iron and aluminum went into making that SUV? How does that compare to my bicycle?

Finally, what are the long-term benefits of cycling over riding? What about better health, both mental and physical, that comes from riding? The savings from not developing heart disease or avoiding the onset of diabetes?

Spring is coming and the riding weather will be better. Since this column began last October, gas prices have dropped by 67%. Before you conclude that it’s too much trouble to commute by bike, think beyond your pocketbook.

Steve Chambers is pedaling (and munching) somewhere.

This article was originally published on February 28, 2009.