One Stone Carbon Reduction Challenge

onestoneAre you ready to reduce your carbon footprint? Not sure where to start? Start here with the One Stone Carbon Challenge!

As you may know, a “stone” is a unit of weight equal to 14 pounds. One hundred fifty-seven stones makes one tonne[1]. I’ve come up with a list of actions that will, on average, reduce your carbon-equivalent[2] output by one stone. Save 157 stones, and you’ve prevented a tonne of carbon from entering the atmosphere. Simple!

Here’s how to play along at home:

  1. Review the list of “one-stone” activities (below).
  2. Print out the Stone Saver Chart (200Kb PNG) and put it on your fridge. You’ll want to calculate how many miles you can drive your car(s) on one stone’s worth of gasoline and make a note of it on the chart.
  3. Every time you take an action that saves one stone of carbon, mark one stone off the chart.
  4. When you’ve marked off the entire chartful of stones, you’ve saved one tonne!
  5. If you can mark off one stone every day, you will save 2 tonnes of carbon each year! See how many charts you can fill up in a year.

More details for the curious:

What’s my carbon footprint?

How are the “stones” calculated?

Stones are calculated through a combination of web-available data from reliable sources, a calculator, and in some cases, a bit of judicious rounding to keep things easy. Some of the figures are directly calculable; some require more complex calculations based on averages of averages. Gasoline, for example, is easy: 1 gallon of gas produces 19 lbs of carbon dioxide emissions. Electricity, though, varies depending on what fuel is used to create it. Coal-fired plants emit much more carbon than nuclear plants; wind energy emits no carbon.

The first calculations

These calculations are based on facts I’ve found from other sources who’ve done their homework, mainly here and this spreadsheet and here.

  • 1 stone = 0.7 gallons of gasoline How many miles is this? Multiply the number of miles per gallon your car gets by 0.7. So, if you get 20 mpg, you can go 14 miles on one stone of gas, but if your car gets 30 mpg, you can go 21 miles on a stone.
  • 1 stone = 1.25 gallons of diesel fuel
  • 1 stone = 28 air miles flown by one person
  • 1 stone = 10 kwh of average US-produced electricity
  • 1 stone = 0.6 gallons of heating oil
  • 1 stone = 1 therm of gas/propane = 100,000 btus = 1.1 gallon of propane = 1.2 ccf natural gas. For the sake of ease, I’m saying 1 stone = 1 gallon of propane or 1 ccf natural gas (ccf = 100 cubic feet; this is the unit of measurement on your gas bill)

The second calculations

Here’s where the fudge factor starts to come in. Using the facts above, I did this second round of calculations around common home energy uses. Many of these facts are “averages of averages” – for example, facts like “the average dryer in the US uses 3.3kwh per load.” If you want to be more precise, track your stones using actual changes in your fuel usage – e.g., this month’s electric bill shows you used 100kwh less than last month, so that’s a 10 stone reduction. However, if you’re more motivated by actions than math, the following will give you some ideas for specific actions you can take to reduce your carbon output.

  • 1 stone = air-drying 3 loads of laundry. The average electric dryer uses 3.3 kwh to dry an average load of laundry. Anything that saves 10 kwh is worth a stone, so you need to not use the dryer for 3 loads. Try hanging your shirts and pants to dry and use the dryer for socks, underwear, and towels. It’s a pretty easy change to make, especially if you have a clothes pole and a bunch of plastic hangers in your laundry room.
  • 1 stone = turning the heat down by 1 degree for a month. Average household uses 1000 therms of heating fuel per year. Turning the heat down 1 degree saves 1% on your heating bill = 10 therms/year = roughly 1 stone per month all year, or 2 stones/month during heating season
  • 1 stone = turning the A/C up by 1 degree for a month. Turning the A/C up 1 degree saves 1-2% on your cooling bill.
  • 1 stone = 1 lb of beef or cheese. Cattle are ruminants and their digestion produces a lot of methane, which is 25 times more potent a greenhouse gas than carbon. Even grass-fed cattle are culprits. This article explains how cattle produce 14 lb of carbon for every pound of meat produced. This article explains that the impact of producing a pound of cheese is roughly equivalent of producing a pound of beef.
  • 1 stone = 3.5 lb of pork [source]
  • 1 stone = 14 lb of chicken [source]
  • 1 stone = 10 lb of local food vs. food that’s been trucked 1500 miles. In Four Season Harvest, Elliot Coleman calculates it takes 2474 btu to truck produce 3200 miles. The average distance US food travels from field to table is 1500 miles = 1162 btu/lb. A gallon of diesel fuel has 139,000 btus and creates 11.3 lb of carbon dioxide. So you can move 119 lb of food per gallon of diesel = 11.3 lb carbon. Which means 0.1 lb of carbon are released to move an average pound of food an average distance from field to table.
  • 1 stone = reducing shower time by 22 minutes. It takes 8btus to heat a gallon of water by 1 degree. Water generally comes into the house at 55 degrees. If your water heater is set at 130 degrees, you need to raise the water temp by 75 degrees = 600 btus per gallon. 56 gallons thusly heated = 34,130 btus = 10 kwh = 1 stone. If you have a low-flow showerhead (and you do, don’t you?), you use 2.5 gallons of 130 degree water per minute, so you’ll use 56 gallons of hot water in 22 minutes. You can save this by showering less often, or taking shorter showers, or turning off the water while you soap up and shampoo your hair. I figure, by taking 5-minute showers instead of my usual 10-minute showers, I save a stone every four days.

Big Savers

  • Replace a 15 year-old fridge with a new Energy Star fridge = 98 stones per year
  • Driving 3 people 350 miles (@25 mpg) round-trip instead of flying = 56 stones
  • Not taking a 350 mile round-trip flight = 25 stones
  • Replacing two 60-watt light bulbs with 15-watt compact fluorescent bulbs (figure it’s on 4 hours per night) = 1 stone per month
  • Unplugging a TV/DVD player when not in use (15 watts of “standby power”) = 1 stone per month

Moving beyond One Stone

If you’re ready to take your carbon savings to the next level, I suggest you check out the Riot4Austerity. We need to get our carbon emissions down to one tonne per person per year, and these are the folks that can help you get there.


1. You notice I’m using “tonne” instead of “ton”; that’s because carbon is usually measured in metric tonnes, or 2200 pounds.

2. Some gasses, like methane, are much more potent greenhouse gasses than carbon dioxide. One tonne of methane is equivalent to 25 tonnes of carbon dioxide. [Source]

See the original blog posting here.

10 thoughts on “One Stone Carbon Reduction Challenge

  1. I can’t imagine the amount of research it took to put together that rock pile of stats. I envy you for all that you learned on the way.

  2. This is great, I would like your permission to adapt it to my classroom. I was thinking of “dropping a stone” for biology, too, after all many of my kids are too heavy as well as myself. I thought we could chart our ‘un-usage’ and gather change for a windmill. It may take a couple years but every kid has loose change and I want to let them make a difference. thanks againfor the page.

    1. Teri- This sounds like a great project! Please feel free to adapt the one-stone challenge to the classroom. E-mail me at for more classroom ideas (I’m an instructional designer by profession). Another idea you might consider – save change for a solar oven. It’s cheaper than a windmill, and you could cook healthy, electricity-free snacks as a class. I found mine at

  3. hold on a minute!
    this new energy star fridge is a great idea, but just how many stones are used in producing it? and what happens to my old fridge? i bet that uses a whole heap of stones in being recycled (thinking optimistically) or just being dumped.
    otherwise, thanks for all the top tips and scary maths! it’s a superb article.

  4. This is an amazing idea. It shows how all the little changes add up. I have bookmarked this page!! I really like your blog, very inspirational. I plan to grow my first veggie garden this year and perserve a lot of food for next winter. Right now I have time to learn how to do it!

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