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MetroMPG 12-13-2007 04:29 PM

Equivalent MPG of cycling - garage feature?
The plan from the start has been to add a Garage feature for cyclists. There are 2 approaches we could take (or both, I guess)
  • A simple comparison, showing the proportion of biking vs. driving
  • Peakster suggested factoring bike (or any hpv) distance travelled in a way that gives "combined" MPG with your car(s). EG. if you got 40 MPG last month in your car, and covered 100 miles, but you also rode 100 miles commuting by bike, your total transportation FE for the month is 80 MPG.
  • Another approach is if your bike computer calculates/estimates energy output, you could just do the math and figure out equivalent FE like I did with the ForkenSwift "MPGe".
How do you figure MPGe for a bike, someone helpfully asks?


I was trying to figure how to come up with a MPG equivalent for the bike, like you did for the ForkenSwift. I have a power meter that gives me the following data:

ave watts
Ave speed
The MPGe formula would simply be distance (mi) / gallons equivalent.

Here's a conversion site that will give you the US gallon equivalent of gasoline in kJ (and lots of other conversions):

1 kilojoule = 0.000,007,589,6 gallon [U.S.] of automotive gasoline

So if you rode 100 miles and the computer said you used 11,300 kJ then your MPGe is...

100 miles/ (11,300 kJ * 0.000,007,589,6 kJ/gal)

or 100 miles / 0.08576248 GALe

= 1166 MPGe

MetroMPG 12-13-2007 04:30 PM

PS - anybody want to check my math? :p

Also, I just kind of picked the kJ figure for going 100 mi. out of a hat, based on one reference I saw after a quick google. It could be wrong.

SVOboy 12-13-2007 04:44 PM

How many people actually have meters that calculate wattage though? Powertap!

MetroMPG 12-13-2007 04:45 PM

And how accurate can they be? What do they measure - heart rate? Body temp?

Lazarus 12-13-2007 04:48 PM

Very nice. I don't know how many will have the computers that will figure kJ so it would probably just be best to use some form of the combine FE. I'm trying to picture how that would work. I guess you would have another column in the garage that has transportation index? Would it be on the rolling 90 day average also?

MetroMPG 12-13-2007 04:53 PM

I like the combined FE idea too.

I figured it would just be for the year. That would be easiest, to start.

It makes for another cool top 10 list, plus it would show in your individual garage.

Lazarus 12-13-2007 04:56 PM


Originally Posted by MetroMPG (Post 2133)
And how accurate can they be? What do they measure - heart rate? Body temp?

Some are pretty accurate. Here's the poop.

SVOboy 12-13-2007 05:06 PM

Powertap actually calculates energy output, that's why they cost 1000 USD and not many people have them, :p

igo 12-13-2007 05:54 PM


Originally Posted by SVOboy (Post 2132)
How many people actually have meters that calculate wattage though? Powertap!

Thats what I was thinking too. I would like to have a month by month bike mileage chart like this:

Route slip has a nice graph based on week to week mileage (it also shows the amount of climbing too, based off of google maps):

If you want to put a more environmental spin on the graph. You could say total mileage by bicycle X,XXXmiles = XX.X gallons saved = X,XXX lbs of CO2 saved.

MetroMPG 12-13-2007 05:54 PM

It's easy to forget how intense cyclists can be until you read something like that. Then again, I'm sure they'd say the same thing about FE nuts after seeing someone who posted a inverview with the inventor of the ScanGauge.

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