Free tool · checked 17 October 2026

Car loan calculator: monthly instalment, interest and EIR

Enter the loan amount, the flat or effective rate you were quoted, the tenure in months and any upfront fees to see the monthly instalment, total interest, total repayable and the effective interest rate (EIR), with the method shown. It also works as an effective interest rate calculator for any instalment loan, and builds in no lender’s rate.

Which rate were you quoted? A flat (add-on) rate An effective interest rate (EIR)

Loan amount (S$)Flat rate (% a year)Tenure (months)Upfront fees, if any (S$)

The starting figures are an illustration, not a quote or a market rate: replace them with the lender’s own figures. Fees here are ones you pay at the start or that are deducted from the loan.

Monthly instalment: S$958.33
Total interest: S$7,500.00
Total repayable (loan plus interest): S$57,500.00
EIR, annual rate with monthly rest (12 × monthly rate): 5.64%
EIR, compounded over a year: 5.79%

How it is worked out

Interest = S$50,000.00 × 3% × 60 ÷ 12 = S$7,500.00. A flat rate charges interest on the original amount for the whole term, even as you repay.
Monthly instalment = (S$50,000.00 + S$7,500.00) ÷ 60 = S$958.33.
EIR: the monthly rate r at which 60 instalments of S$958.33 repay S$50,000.00, the r that solves loan = instalment × (1 − (1 + r)^−60) ÷ r. The tool finds it by bisection, halving the range of possible rates until it is far narrower than the decimals shown: r = 0.4701% a month.
EIR as an annual rate with monthly rest: 12 × r = 5.64%. Compounded over a year: (1 + r)^12 − 1 = 5.79%.

A 3.00% flat rate as an EIR, by tenure

Tenure	Flat rate	EIR (12 × monthly rate)	EIR (compounded)
1 year	3.00%	5.49%	5.63%
2 years	3.00%	5.66%	5.81%
3 years	3.00%	5.68%	5.83%
4 years	3.00%	5.67%	5.82%
5 years (yours)	3.00%	5.64%	5.79%
6 years	3.00%	5.61%	5.76%
7 years	3.00%	5.57%	5.72%

The last instalment is S$958.53 so that the instalments add up to S$57,500.00.

Rounding is the tool’s convention: interest and the instalment are rounded to the nearest cent, half a cent up, and any difference goes on the last instalment. A lender’s schedule may round differently by a few cents.

The EIR is shown two ways because lenders and guides do not all compute it the same way. Ask the lender which method its quoted EIR uses before you compare it with this one.

Arithmetic only: no lender’s rate, rule or loan limit is built in. The table excludes fees. Percentages are rounded to 2 decimal places, which is the tool’s convention. Nothing you type leaves your browser.

What this tool does not use

This tool applies no official rate or rule: it only does arithmetic on the figures you enter, and the guide below states its rounding convention.

Next review: No outside rule or rate is used. By 17 April 2027, try again to open MAS’s and MoneySense’s pages on EIR disclosure and car loan limits, and add a fact only from a page actually read; rerun the solver tests after any change to the arithmetic. General information, not tax, legal or financial advice.

How is a car loan instalment worked out with a flat rate?

A flat (add-on) rate charges interest on the original loan for the whole tenure, even as the balance falls. Interest is the loan times the flat rate times the years; add it to the loan and divide by the number of months. Our illustration, not a quote or a market rate: S$50,000 at 3% flat over 60 months carries S$50,000 × 3% × 5 = S$7,500 of interest, so S$57,500 is repaid in 60 instalments of S$958.33, the last one S$958.53 after rounding.

How is the effective interest rate (EIR) calculated?

The EIR states the same loan as a rate charged only on what you still owe. The tool finds the monthly rate r at which the instalments exactly repay the loan, solving loan = instalment × (1 − (1 + r)^−n) ÷ r for n months by bisection: it tries a rate, checks whether the instalments are worth more or less than the loan, and halves the range each time. In the example r is 0.4701% a month: 5.64% a year as 12 × r, or 5.79% compounded, (1 + r)^12 − 1.

Which EIR figure should I compare?

Lenders and guides do not all use the same method, which is why the tool shows both. Ask the lender for its EIR in writing and how it is worked out, then compare like with like; if you enter a quoted EIR, pick the matching option. We tried to open MAS’s and MoneySense’s pages on EIR and car loans on 17 October 2026 and could not, so this tool states no rule on how lenders must disclose the EIR and no limit on car loans.

Why is the EIR almost double the flat rate?

Our explanation: you pay interest on the full amount for the whole tenure, yet on average you owe only about half of it. At 3% flat the EIR (12 × r) is 5.49% over 1 year, 5.68% over 3 years, 5.64% over 5 years and 5.57% over 7 years; the table in the tool repeats this for any rate. A longer tenure lowers the instalment but raises the total interest: at 3% flat, S$50,000 costs S$7,500 over 5 years and S$10,500 over 7.

How do fees change the EIR?

Processing or administration fees paid at the start mean you receive less but repay the same instalments. The tool treats them that way and solves again: in the example, a S$500 fee raises the EIR from 5.64% to 6.06% (12 × r) and the total cost of borrowing to S$8,000. If a fee is added to the loan instead, include it in the loan amount and enter it as a fee too.

What does this calculator not do?

It knows no lender’s rates, fees or terms and states no market rate. It does not model early repayment, late charges, insurance, a balloon payment or limits on loan size or tenure, and it does not say whether a loan is affordable. Rounding the instalment and interest to the nearest cent (half a cent up, any difference on the last instalment) and percentages to 2 decimal places are our conventions; a lender’s schedule may differ by a few cents. Our buy-now-pay-later guide applies the same full-cost check to short instalment plans, and the total price check covers the rest of a purchase.

Common questions

How do I convert a flat rate to an effective interest rate?

Work out the instalment from the flat rate, then find the monthly rate at which those instalments repay the loan. At 3% flat over 5 years the EIR is 5.64% (12 × r) or 5.79% compounded.

How is a monthly car loan instalment calculated?

With a flat rate, add the loan and the flat interest (loan × rate × years) and divide by the months. S$50,000 at 3% flat over 60 months gives S$958.33 a month (our illustration).

Why does a 7-year loan cost more than a 5-year loan at the same flat rate?

Flat interest is charged for every year of the tenure. At 3% flat on S$50,000 it is S$7,500 over 5 years and S$10,500 over 7 years, although the monthly instalment is lower.

Is anything I type sent anywhere?

No. The sums are worked out in your browser.

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