How to use the oil change interval calculator
- Enter the odometer at your last change and the interval in miles that you follow. The starting 5,000 is an example, so use the one from your owner manual or your shop.
- Optionally enter the odometer now to see how many miles are left, and the miles you drive a month to estimate the date you will reach the due mileage.
- If your plan also has a time limit, enter the date of the last change and the interval in months. Today's date is filled in for you and can be changed.
- Read the due mileage, the miles left or past due, the dates, and which comes first. Use Copy, Print or CSV to keep the result.
Formula
Due mileage = odometer at last change + interval in miles
Miles left = due mileage - odometer now
Days until due mileage = miles left / miles per month x 365 / 12, rounded up
Due by time = date of last change + interval in months
When both a mileage and a time limit apply, the change is due at whichever comes first.
Last changed at 40,000 miles
If your last oil change was at 40,000 miles and you change every 5,000 miles, the next one is due at 45,000 miles. With the odometer now at 43,500, you have 1,500 miles left.
Driving 800 miles a month, 1,500 miles takes 1,500 / 800 x 365 / 12 = 57.0 days, rounded up to 58 days. From October 10, 2026 that is December 7, 2026. If the last change was on June 15, 2026 and you also change every 6 months, the time limit is December 15, 2026, so mileage comes first. With the odometer at 41,000 and only 100 miles a month, time comes first.
Miles, months or both
Many plans use both a distance and a time limit because oil breaks down with age even if the car is barely driven. Drivers who cover a lot of miles reach the mileage first, and drivers who cover few miles reach the months first. The tool shows both so you can see which one matters for you.
The intervals you enter are your own. Your owner manual, the type of oil and your driving conditions, such as short trips, dust, towing or extreme temperatures, decide the right interval for your vehicle. The calculator does not know any of these.
Keeping track
Write the odometer reading and date on the invoice and keep it with your records. A printed schedule makes it easy to see all of your maintenance in one place: the car maintenance schedule printable covers oil, filters, tires and more.
To track how much you drive, a vehicle mileage log is useful, and the total cost of car ownership calculator shows what upkeep adds to the yearly cost of the vehicle. The MPG calculator is helpful for fuel economy.
Assumptions and limits
- The interval and the dates are what you enter. The tool does not know your vehicle or its manufacturer recommendations.
- A month is treated as 365 / 12 days when estimating the date from miles.
- Driving is assumed to continue at the pace you enter. A trip or a change of routine moves the date.
- The odometer now cannot be lower than the reading at the last change.
Frequently asked questions
How do I calculate when my next oil change is due?
Add the interval to the odometer reading at the last change. A change at 40,000 miles with a 5,000 mile interval is due at 45,000.
How often should I change my oil?
That depends on your vehicle and the oil, so follow your owner manual or ask your shop. The interval is an input here because this tool cannot know it.
What if I use both miles and months?
Enter both. The tool calculates each due date and tells you which comes first when it has enough information to estimate the mileage date.
Why is the date an estimate?
It assumes you keep driving at the same pace each month. Longer trips or less driving move the real date.