Test extra monthly payments and a lump sum against your car loan.
| Plan | Months | Interest |
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Assumes a simple interest loan where interest is charged monthly on the balance at APR ÷ 12, and overpayments reduce the balance straight away. Precomputed interest loans and some PCP deals work differently, so ask your lender for a settlement figure.
This auto loan interest saver calculator shows car owners in the UK, US or Europe how much interest they save, and how many months sooner they finish, by paying extra each month or clearing a lump sum off their car loan. The Consumer Financial Protection Bureau's auto loan guides are a good companion if you are in the US, while UK readers should check their credit agreement for early repayment terms.
Quick answer: An auto loan interest saver calculator runs your car loan twice, once as agreed and once with overpayments, because each month's interest is the balance × APR ÷ 12. Paying an extra £100 a month on an £18,000 loan at 7.9% over 60 months saves about £995 of interest and finishes 15 months early.
In This Guide
What Is an Auto Loan Interest Saving?
An auto loan interest saving is the difference between the total interest you would pay by sticking to the contract and the total you pay after making overpayments. On a simple interest car loan, each month's interest is the balance × APR ÷ 12, so every pound of overpayment stops attracting interest from the day it lands.
Your contractual payment stays the same, which means the loan ends earlier rather than the payment falling. The calculator runs the loan month by month twice, once as agreed and once with your overpayments, then subtracts any early repayment fee from the saving.
How to Use the Auto Loan Interest Saver Calculator
Step 1: Enter Your Loan Details
Pick your currency, then enter today's balance from your latest statement, the APR on your agreement and the number of payments left. The default 7.9% is only an example rate.
Step 2: Add Your Overpayments
Type a regular extra monthly amount, a one off lump sum such as a bonus or tax refund, or both. Set either to zero to see its effect on its own.
Step 3: Allow for an Early Repayment Fee
Most simple interest loans charge nothing. On UK hire purchase and personal loans, the MoneyHelper guide to ending car finance early explains that any charge is capped at 1% of the amount repaid early, or 0.5% with under 12 months left, and should not apply to early repayments under £8,000.
Step 4: Compare the Plans
The headline shows your net interest saving and the new finish date. The table compares no overpayments, extra monthly only, lump sum only and both, so you can see which does the heavy lifting.
How Much Interest Do I Save by Paying Extra on a Car Loan?
An extra £100 a month on an £18,000 car loan at 7.9% over 60 months saves about £995 of interest and finishes 15 months early. Marcus, a delivery driver in Leicester, has exactly that loan with a £364.11 monthly payment and £3,847 of interest still to come. Here is how his options compare:
| Marcus's plan | Months to clear | Total interest | Saving |
|---|---|---|---|
| No overpayments | 60 | £3,847 | £0 |
| £1,000 lump sum now | 56 | £3,379 | £468 |
| £100 extra a month | 45 | £2,852 | £995 |
| £100 extra plus £1,000 now | 43 | £2,517 | £1,330 |
| £200 extra a month | 36 | £2,272 | £1,575 |
Regular extra payments beat a one off lump sum here because £100 a month adds up to far more than £1,000 over the loan. If a cheaper rate is on offer, the loan calculator shows what refinancing the balance would cost. On a balloon deal, use the PCP calculator instead, because the final payment changes the maths, and keep an emergency buffer before you overpay anything.
Auto Loan Interest Saver Terms Explained
These definitions explain the loan mechanics behind the auto loan interest saver calculator, so you can see exactly why overpaying cuts your total interest.
- Annual percentage rate (APR)
- The yearly cost of borrowing expressed as a percentage, including interest and compulsory fees. On a simple interest car loan, dividing it by 12 gives the monthly rate applied to the outstanding balance.
- Simple interest loan
- A loan where interest is charged only on the balance still owed each month, never on previously charged interest. Every overpayment therefore stops costing interest immediately, unlike loans where the interest is fixed at the start.
- Amortisation
- The gradual repayment of a loan through regular instalments that cover that month's interest plus a slice of the balance. Early payments are interest heavy, which is why overpaying near the start of a term saves the most.
- Overpayment
- Any amount paid above the contractual instalment, either as a regular monthly extra or a one-off lump sum. With the payment unchanged, overpaying shortens the term rather than lowering future instalments.
- Early repayment charge
- A fee a lender may apply when a loan is cleared or reduced ahead of schedule. For UK regulated credit it is capped at 1% of the amount repaid early, or 0.5% when under 12 months remain.
- Personal contract purchase (PCP)
- A car finance agreement with lower monthly payments and a large optional final payment, often called a balloon. Because that final sum is fixed, overpaying works differently from a standard amortising loan.
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How we checked this tool: the Tools Veria Editorial Team built this tool by hand, checked it against the official rules or published standards where they apply, and tested it against worked examples. Results are estimates for planning, not personal financial or tax advice. Read our editorial policy and disclaimer, or report an error.
Frequently Asked Questions
Is it better to pay extra monthly or a lump sum on a car loan?
Both save the same interest per pound if paid at the same time, but money paid earlier saves more. An extra £100 a month on an £18,000 loan at 7.9% saves £995, while a single £1,000 payment now saves £468.
Does paying extra on a car loan lower my monthly payment?
Usually not. Most lenders keep the contractual payment the same and shorten the term instead, so you finish sooner. Some UK lenders let you choose a lower payment after a partial settlement, so ask yours.
Can I be charged for paying off a car loan early in the UK?
Yes, but the charge is capped. Under the Consumer Credit Act it cannot exceed 1% of the amount repaid early, or 0.5% if less than 12 months remain, and MoneyHelper says no charge should apply to early repayments under £8,000.
What is a precomputed interest car loan?
A precomputed loan fixes the total interest at the start and front loads it, often using the Rule of 78. Paying extra saves less than on a simple interest loan, so ask your lender for an exact payoff figure.
Should I overpay my car loan or save the money?
Overpay only after you have an emergency fund of three to six months of essential costs. A loan at 7.9% APR usually costs more than a savings account earns, so overpaying is then a guaranteed return.
How do I tell my lender the extra is an overpayment?
Contact the lender in writing or through its app and ask for the money to reduce the principal, not to prepay future instalments. Otherwise some lenders simply hold it as an advance payment and interest keeps running.