Carpooling Savings Calculator
See how much each person saves by carpooling instead of driving alone.
Last updated · View algorithm, constants and default inputs (JSON)
About this calculator
Per-person estimate in US dollars (USD), assuming 52 commuting weeks and an equal split of modeled fuel, wear and daily parking/tolls. It assumes each rider would otherwise drive alone on the same route; detours and actual shared costs are not modeled. CO₂ is an estimated gasoline tailpipe comparison.
Worked example
calculated with the default values below
Round trip commute distance 40 mi · Commute days per week 5 days · Fuel economy 28 mpg · Fuel price 3.5 USD/US gal · People sharing 3 · Running cost per mile (wear, tyres) 0.12 USD/mi · Parking or tolls per day 10 USD/day Annual saving 3,432 USD · Commute miles per year 10,400 mi · Annual cost driving alone 5,148 USD · Your annual share 1,716 USD · Estimated gasoline tailpipe CO2 avoided per person/year 4,851 lb
General background references
Disclaimer
These calculators give estimates for general information only. Real fuel consumption, performance and range vary with driving style, load, terrain, temperature and vehicle condition. Do not rely on these results for towing limits, payload or braking decisions — use the rating plate of your vehicle.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
S = C × (1 − 1 ÷ k), C = 52 w (d t + p)
- S
- Annual saving
- C
- Annual solo-driving cost
- k
- Number of riders
- w
- Commute days per week
- d
- Round-trip miles per day
- t
- Per-mile fuel and wear
- p
- Daily parking cost
Annual miles = round-trip miles × commute days × 52. Annual modeled costs divide fuel, wear and daily parking/tolls equally among riders. CO₂ uses 8,887 g per US gallon and assumes every rider otherwise drove alone on the same route; it is a tailpipe estimate.
Frequently asked questions
How is the per-person saving and CO2 estimate calculated?
The solo annual route cost is divided equally among riders, assuming each would otherwise make the same trip alone. The CO2 estimate assumes gasoline and applies the EPA tailpipe factor of 8,887 g CO2 per US gallon to the trips replaced; it excludes upstream fuel emissions and vehicle differences. Actual savings depend on whether extra solo trips are truly avoided.