Use this free pro rata mileage calculator to check whether your car lease, PCP, or work mileage is on track before unexpected charges catch you out. Whether you are in the UK or the US, enter your contract details and get a clear breakdown in seconds.
Pro rata mileage is one of those things most drivers never think about until the final bill arrives. By that point, fixing it is expensive. This guide explains exactly how it works, how to calculate it yourself, and what to do if you are over your allowance.
What Is a Pro Rata Mileage Calculator?
A pro rata mileage calculator works out how many miles you should have driven by a specific point in your lease or finance agreement, based on the fraction of the contract that has elapsed. Pro rata simply means proportional your allowed mileage at any given moment is proportional to how far through the contract you are.
For a car lease or Personal Contract Purchase (PCP) agreement, exceeding this allowance even mid-contract can trigger financial penalties when you hand the car back or settle early. In a workplace context, a pro rata mileage calculation ensures employees are reimbursed fairly based on the exact distances driven, rather than a flat monthly estimate.
How to Calculate Pro Rata Mileage
The core formula is straightforward:
Daily Allowance = Annual Mileage Allowance divided by 365
Pro Rata Allowed Miles = Daily Allowance multiplied by Days Elapsed
Excess Mileage = Actual Miles Driven minus Pro Rata Allowed Miles
Step-by-Step Calculation
Working this out manually takes five steps:
- Find your daily allowance. Divide your contracted annual mileage by 365. If your contract allows 10,000 miles per year, your daily rate is 27.4 miles per day.
- Count the days elapsed. Count calendar days from your contract start date to today, including both the start and end dates.
- Calculate your pro rata target. Multiply the daily allowance by the number of days elapsed. At day 180 with a 10,000-mile allowance, your target is 4,932 miles.
- Find your actual mileage driven. Subtract your delivery mileage from your current odometer reading. This removes any pre-existing miles from the count.
- Compare and calculate any excess. Subtract your pro rata target from your actual miles. A positive result means you are over; a negative result means you have miles in reserve.
Worked Example UK Lease
A UK driver on a 12-month lease with 10,000 miles per year and an excess mileage charge of 12p per mile (plus VAT):
- Contract start: 1 January 2025
- Check date: 1 July 2025 (day 181)
- Delivery mileage: 10 miles
- Current odometer: 6,200 miles
- Actual miles driven: 6,190
Daily allowance: 10,000 divided by 365 = 27.4 miles per day
Pro rata target: 27.4 multiplied by 181 = 4,959 miles
Excess: 6,190 minus 4,959 = 1,231 miles over
Estimated charge: 1,231 multiplied by £0.12 = £147.72 (before VAT)
This is the kind of surprise bill that catches thousands of UK drivers every year. According to standard leasing industry practice, excess mileage charges typically range from 3p to 30p per mile depending on the vehicle tier and provider.
Worked Example US PCP / Lease
A US driver on a 36-month lease with 12,000 miles per year (36,000 total) and an overage charge of $0.15 per mile:
- Lease start: January 2025
- Check date: July 2025 (180 days)
- Odometer at delivery: 8 miles
- Current odometer: 6,500 miles
- Actual miles driven: 6,492
Daily allowance: 12,000 divided by 365 = 32.88 miles per day
Pro rata target: 32.88 multiplied by 180 = 5,918 miles
Excess: 6,492 minus 5,918 = 574 miles over
Estimated charge: 574 multiplied by $0.15 = $86.10
The Federal Trade Commission requires that US lease agreements disclose excess mileage charges clearly in the lease terms. Most major lenders follow guidelines consistent with Consumer Financial Protection Bureau recommendations.
UK-Specific Rules: What You Need to Know
HMRC Mileage Rates for Work Travel
If you use your own car for work journeys, HMRC’s Approved Mileage Allowance Payments (AMAPs) define the tax-free amounts your employer can reimburse:
- Cars and vans: 45p per mile for the first 10,000 miles per tax year; 25p per mile thereafter
- Motorcycles: 24p per mile
- Bicycles: 20p per mile
These rates apply whether you drive 10 miles or 10,000 miles in a year. If your employer pays less than these rates, you can claim Mileage Allowance Relief through HMRC. If they pay more, the excess is taxable. Visit GOV.UK for the current official rates.
Is Mileage Still 45p Per Mile in 2025?
Yes. As of 2025/26, the HMRC approved rate for cars and vans remains 45p per mile for the first 10,000 miles per tax year, unchanged since 2011. Many commentators have called for an increase given rising fuel and vehicle costs, but HMRC has not updated these figures. The 25p rate above 10,000 miles also remains in force.
Does 45p Per Mile Cover Wear and Tear?
The 45p rate is designed to cover fuel, oil, tyres, servicing, insurance, and depreciation not just fuel. Whether 45p adequately covers wear and tear depends on the vehicle type, fuel cost, and typical maintenance profile. Electric vehicle drivers may find the rate generous given lower fuel costs; diesel or high-mileage drivers may find it tight. ACAS confirms that employers are not legally required to pay the full AMAP rate, but employees can claim tax relief on the shortfall.
Excess Mileage on UK Car Leases and PCPs
Under UK consumer contract law, excess mileage clauses are enforceable and must be disclosed clearly before signing. The Financial Conduct Authority (FCA) regulates PCP and HP agreements and requires lenders to treat customers fairly. If you are in financial difficulty and facing unexpected excess charges, contact your lender before the end of the contract many will negotiate a mid-contract adjustment, which may be cheaper than paying per-mile penalties.
US-Specific Rules: What American Drivers Need to Know
IRS Standard Mileage Rate
The IRS updates the standard mileage rate annually. For 2025, the business mileage rate is 70 cents per mile. This rate covers all operating costs including fuel, depreciation, insurance, and maintenance, and can be used instead of tracking actual vehicle expenses.
You can claim the IRS standard mileage rate by keeping a mileage log that records the date, destination, business purpose, and miles driven for each trip. The IRS Publication 463 provides full guidance on travel expense deductions.
Excess Mileage on US Auto Leases
Most US auto leases set a mileage allowance of 10,000 to 15,000 miles per year. Excess charges of $0.10 to $0.25 per mile are standard. The Consumer Leasing Act requires that these charges be disclosed in the lease agreement. Some lenders allow you to purchase additional miles upfront at a lower per-mile rate always compare this against your actual usage before signing.
How Do I Calculate My Mileage Reimbursement?
Multiply the number of miles driven by the applicable rate. If you drove 342 miles at the IRS rate of $0.70, your reimbursement is $239.40. For HMRC rates, the same trip at 342 miles using 45p per mile gives £153.90. The calculator handles both scenarios automatically, including the HMRC threshold calculation for the 10,000-mile step-down.
What Is 25k Pro Rata at 30 Hours?
This question combines two different types of pro rata calculation. If a full-time salary is £25,000 per year for a 37.5-hour working week, and your contracted hours are 30 per week, your pro rata salary is:
£25,000 multiplied by (30 divided by 37.5) = £20,000 per year
This is a salary calculation rather than a mileage calculation. For mileage, the same proportional logic applies if your annual allowance is 25,000 miles but you work part-time hours, your pro rata mileage budget may be adjusted accordingly. The calculator includes a part-time factor field for exactly this situation.
Tips to Avoid Excess Mileage Charges
Check your mileage monthly. Set a recurring reminder and compare your actual odometer against the pro rata target. Catching an overrun early gives you time to adjust.
Use the daily rate as a habit. If your daily allowance is 27 miles, a quick check of whether today’s journey keeps you on track takes seconds.
Negotiate upfront, not at the end. If you know your mileage will be high, buy additional miles at the start of the agreement. Upfront rates are almost always cheaper than end-of-contract excess charges.
Contact your provider early if you are over. Many UK lenders will arrange a mid-contract mileage adjustment. The monthly premium for additional miles is usually much lower than the per-mile excess rate.
Consider a higher-mileage contract. If you consistently exceed your allowance, it may be cheaper to move to a higher annual mileage tier from the start.
Related Calculators
For salary pro rata calculations, see our Pro Rata Salary Calculator. For holiday entitlement, use our Pro Rata Holiday Calculator. If you are calculating school term-time pay, our Pro Rata Term Time Salary Calculator covers that scenario in detail.
Frequently Asked Questions
What does pro rata mileage mean?
Pro rata mileage means the number of miles you are allowed to have driven at a specific point in your contract, proportional to how far through the agreement you are. If your annual allowance is 12,000 miles and you are six months in, your pro rata allowance is 6,000 miles.
How do I calculate pro rata mileage for a car lease?
Divide your annual mileage allowance by 365 to get your daily rate. Multiply the daily rate by the number of days since the contract started. Subtract your delivery mileage from your current odometer. If the result is higher than your pro rata allowance, you are in excess.
Is mileage still 45p per mile in the UK?
Yes, as of the 2025/26 tax year HMRC’s approved rate for car and van mileage remains 45p per mile for the first 10,000 miles, then 25p per mile. These rates have not changed since 2011.
Does 45p per mile cover wear and tear?
The 45p HMRC rate is intended to cover all motoring costs including fuel, oil, servicing, tyres, insurance, and depreciation. Whether it fully covers wear and tear depends on your vehicle type and actual running costs.
How do I calculate my mileage reimbursement in the UK?
Multiply the number of business miles driven by the HMRC approved rate. For the first 10,000 miles in a tax year, use 45p per mile. Above 10,000 miles, use 25p. The calculator automatically applies the correct threshold based on your year-to-date mileage.
What is the excess mileage charge on a UK lease?
Excess mileage charges on UK leases typically range from 3p to 30p per mile (plus VAT), depending on the vehicle tier and provider. The exact rate is stated in your contract. Multiply the number of excess miles by this rate to estimate your liability.
What is the IRS standard mileage rate for 2025?
The IRS business mileage rate for 2025 is 70 cents per mile. This rate applies to business travel in a personal vehicle and covers all operating costs. Check IRS.gov for the most current figures.
Can I buy additional miles on a car lease?
Yes. Most UK and US lenders allow you to purchase additional miles upfront at a reduced per-mile rate compared to end-of-contract excess charges. Contact your provider before the contract ends or ideally at signing if you anticipate high mileage.
What happens if I exceed my mileage allowance on a PCP?
On a PCP, if you exceed your contracted mileage you will be charged per mile at the rate specified in your agreement when you hand the car back. If you are settling early, the lender may calculate excess charges up to the point of settlement. Contact your lender early many will negotiate.
How is pro rata mileage different for part-time workers?
If you work part-time, your mileage allowance may be pro-rated to reflect your working hours relative to a full-time equivalent. For example, if a full-time driver is allowed 20,000 miles per year and you work 60% of full-time hours, your pro rata allowance may be 12,000 miles. The calculator includes a part-time factor field for this.