Car Share Membership vs Used Car Ownership Cost Calculator
How This Car Share vs Used Car Cost Calculator Helps You
This calculator is designed for drivers who are deciding between paying for a car share membership and buying a used car of their own. It adds up membership fees, per-mile charges, and ownership costs so you can see which option is cheaper for the way you actually drive.
You enter your expected monthly mileage, the car share pricing you have access to, and the key costs of owning a used car. The tool then estimates:
- Total cost of car sharing over your chosen ownership period
- Total cost of owning and operating a used car over the same period
- Approximate cost per mile for each option
- The break-even mileage where both options cost about the same
By putting both options into the same units (dollars over the same time frame and per-mile costs), the calculator gives you a clearer financial comparison than marketing claims or rules of thumb like “owning is always cheaper if you drive a lot.”
Formulas Used in the Calculator
The calculator works by translating all costs into total dollars over the ownership period, based on the number of miles you expect to drive. The main building blocks are:
- Monthly car share cost
- Monthly used car ownership cost
- Break-even monthly mileage
Car Share Total Cost
If you drive M miles per month and the membership fee is F dollars per month with a per-mile rate of S, then the monthly car share cost is:
Car share monthly cost = F + S × M
Over an ownership period of Y years:
Car share total cost = (F + S × M) × 12 × Y
Used Car Ownership Total Cost
For a used car, there are both fixed and variable costs. The main components are:
- Depreciation: purchase price minus resale value, spread over the period
- Maintenance: annual maintenance costs
- Insurance: annual insurance premiums
- Parking: monthly parking or permit costs
- Fuel: cost per mile times miles driven
Let:
- P = used car purchase price
- R = expected resale value after Y years
- Y = ownership period in years
- Am = annual maintenance cost
- Ai = annual insurance cost
- Pm = monthly parking cost
- Fu = fuel cost per mile
- M = miles driven per month
Depreciation over the entire period is:
Depreciation = P - R
Total ownership cost over Y years is then approximated as:
Used car total cost = (P - R)
+ Am × Y
+ Ai × Y
+ Pm × 12 × Y
+ Fu × M × 12 × Y
Break-Even Mileage (MathML)
The break-even mileage is the monthly mileage M at which the total cost of car sharing and owning a used car are equal. To find it, we set the monthly costs equal and solve for M. In MathML form, the monthly break-even mileage can be written as:
Where:
- M = break-even miles per month
- P = purchase price
- R = resale value after Y years
- Y = ownership period in years
- Am = annual maintenance cost
- Ai = annual insurance cost
- Pm = monthly parking cost
- F = monthly car share membership fee
- S = car share cost per mile
- Fu = fuel cost per mile for the used car
The numerator represents the monthly fixed cost of owning a car (including depreciation, maintenance, insurance, and parking) minus the car share membership fee. The denominator is the difference between the car share per-mile price and your fuel cost per mile for the used car.
How to Interpret the Results
When you run the calculator, you will typically see:
- Total cost of car sharing over the selected ownership period
- Total cost of used car ownership over the same period
- Average cost per mile for each option
- An estimated break-even mileage per month
If your actual monthly mileage is below the break-even mileage, car sharing will usually be cheaper on a purely financial basis. If your mileage is above the break-even point, owning a used car will typically be cheaper per mile.
You can also experiment with different scenarios:
- Increase fuel prices to see how sensitive ownership costs are.
- Change the ownership period to reflect how long you keep cars.
- Adjust maintenance to reflect an older or more reliable vehicle.
- Try different car share programs with different membership fees.
Treat the break-even mileage as an approximate threshold, not an exact prediction. Real-world costs can vary from month to month.
Worked Example
Suppose you are considering either joining a car share service or buying a used car. Assume the following numbers:
- Car share membership fee: $20 per month
- Car share cost per mile: $0.45
- Miles driven per month: 500
- Used car purchase price: $10,000
- Resale value after ownership: $4,000
- Ownership period: 5 years
- Annual maintenance cost: $800
- Annual insurance cost: $900
- Fuel cost per mile: $0.15
- Monthly parking cost: $50
Car Share Costs
Monthly cost:
= 20 + 0.45 × 500
= 20 + 225
= $245 per month
Over 5 years:
= 245 × 12 × 5
= 245 × 60
= $14,700 total
Used Car Costs
Depreciation:
= 10,000 - 4,000 = $6,000
Maintenance over 5 years:
= 800 × 5 = $4,000
Insurance over 5 years:
= 900 × 5 = $4,500
Parking over 5 years:
= 50 × 12 × 5 = 50 × 60 = $3,000
Fuel over 5 years (500 miles per month):
= 0.15 × 500 × 12 × 5 = 0.15 × 30,000 = $4,500
Total used car cost:
= 6,000 + 4,000 + 4,500 + 3,000 + 4,500
= $22,000
In this example, at 500 miles per month over 5 years, car sharing would cost about $14,700, while owning the used car would cost about $22,000. For this mileage and set of assumptions, car sharing is cheaper. If you increase the monthly miles, ownership will gradually become more attractive relative to car sharing.
Cost Comparison Summary
The table below summarizes how the calculator compares car share and used car ownership on a cost basis.
| Aspect | Car Share Membership | Used Car Ownership |
|---|---|---|
| Main cost structure | Monthly membership fee plus per-mile rate | Upfront purchase, depreciation, plus ongoing running costs |
| Fixed monthly costs | Membership fee only | Depreciation, insurance, parking, and part of maintenance |
| Variable costs | Per-mile price (includes fuel and maintenance) | Fuel per mile and additional wear-related maintenance |
| Best suited for | Low-mileage or occasional drivers | Moderate to high-mileage drivers who use a car frequently |
| Cost visibility | Easy to see cost per trip | Costs spread across multiple bills and time periods |
| Break-even concept | Becomes more expensive above the break-even monthly mileage | Becomes cheaper per mile once you exceed the break-even mileage |
Assumptions and Limitations
This calculator is a simplified model to help you compare major, predictable costs. It does not capture every possible expense or benefit. Keep the following assumptions and limitations in mind when you use the results.
- Constant prices: The model assumes that fuel costs, maintenance, insurance, and car share rates remain constant over the ownership period. In reality, these can rise or fall.
- No financing costs: Interest on car loans, financing fees, and opportunity cost of tying up cash in a car purchase are not included. The model treats the purchase price and resale value as cash-based, not financed.
- Taxes and fees: Registration fees, sales taxes, vehicle inspections, emissions tests, and traffic tickets are excluded. If these are significant where you live, you may want to add them to your ownership cost estimates.
- Uniform usage: The model assumes you drive roughly the same number of miles every month. Seasonal or irregular usage can make real-world costs deviate from the estimates.
- Simple car share pricing: Many services use tiered pricing, time-based charges, or bundled mileage. The calculator reduces this to a single membership fee plus a per-mile rate, so you may need to approximate your effective rate.
- Car condition: Maintenance costs can vary widely based on vehicle age, brand, and condition. The input for annual maintenance is an average; unexpected repairs are not modeled separately.
- Non-financial factors: Time spent parking, flexibility, convenience, and the comfort of always having a car are important but are not quantified here. Likewise, environmental impact differences are not calculated.
Use the calculator as a decision-support tool rather than a precise budget. If you want a more conservative estimate, you can try rerunning the calculation with higher maintenance and fuel costs, or a lower resale value, to see how sensitive the comparison is to less favorable assumptions.
Related calculators: Car vs Rideshare vs Transit Cost Calculator and Used Car Reliability Cost Estimator.