How do I measure my commute's carbon footprint with mixed driving?

[BrandonPS]

I’m trying to figure out how to actually measure the carbon footprint of my daily commute, because my drive is a mix of highway and stop-and-go city traffic. I have the total mileage, but I’m not sure if that’s enough to get a meaningful number or if the type of driving changes things significantly.

[Oliver35]

One thing I learned was that total miles alone doesn’t tell you much. I split my commute into city and highway portions for a week, wrote down miles and tank fuel, and then used a simple calc: city miles divided by city mpg plus highway miles divided by highway mpg to estimate fuel used. It was rough, but it lined up with my tank refills enough to feel real. The stop-and-go part mattered a lot more than I expected, and idling time adds up.

[Dennis74]

I tried an app that logs trips and fuel purchases, but the numbers varied by day. Short trips with frequent stops dragged the average way down, and the longer highway legs pulled it up. It helped me see that the mix matters, but it was a pain to keep consistent. I ended up using the simple city/highway split most weeks and just accepted a rough estimate.

[William_M]

I kept asking if the problem is actually the route or the car’s efficiency. After a couple weeks I swapped to a more efficient car for a week and noticed the numbers dropped a bit, but then realized a lot of the gain came from tires, weight, and weather. It felt easy to blame the commute, but the data pointed to the car plus stop time as big levers. I still didn’t settle on a single best approach.

[Natalie30]

Sometimes I drifted from the numbers to whether it even matters to track it exactly. I thought about trying to quantify every day, but I failed to keep up. Maybe what matters more is a trend over a few weeks, or comparing options like carpool or biking, rather than nailing a precise figure. Do you actually need a precise number, or is a directional sense enough?