The annual percentage rate (APR) is a Very Important Number.
If you are a borrower, it is the one number you should use when comparing loan offers.
If you are a lender in the United States, you must disclose the APR by providing potential borrowers with a Regulation Z APR Disclosure Statement in order not to run afoul of the law. (See who must prepare a disclosure statement below.)
This calculator will calculate the APR for any closedend loan as well as create a compliant TruthinLending Act disclosure statement.
Let's get started. More below
Info...
What is Annual Percentage Rate or APR?
The Consumer Protection Financial Bureau paraphrases the Truth In Lending Act (TILA) of 1968, which says the "annual percentage rate is the cost of credit expressed as a yearly rate in a percentage."
What is the difference between an interest rate and the annual percentage rate?
Again, I'll paraphrase from the CPFB:
A loan's interest rate is the cost you pay each year to borrow money expressed as a percentage. The interest rate does not include fees charged for the loan.
The annual percentage rate is the cost you pay each year to borrow money, including fees, expressed as a percentage. Therefore, the APR is (basically) the rateofreturn earned by the lender.
Rateofreturn?
Yes! From the lender's perspective. Remember, the loan is the lender's investment and all investor's hope to make a return.
What's important for the borrower to remember, is the lower the APR, the less the loan will cost, which makes sense. The lower the rateofreturn for the lender, the less profit they are earning on the loan they issue.
Why should a borrower compare APRs and not interest rates?
The APR was created by the TILA to give borrowers a way to compare loans.
Why can't I just compare the interest rate of two loans and select the loan with the lowest rate?
Good question, and here's why.
If you wanted to compare two loans using their quoted interest rates, you would have to know and understand a lot of details about how the interest rate is used to calculate each loan's interest.
For example, you would have to know:
 each loan's compounding frequency;
 the daysperyear used for odd day interest calculations;
 the interest allocation method for short or long periods; and
 the impact of fees
Once you understand these details, then you would be able to calculate the interest due and compare the results.
Aside from fees, the APR isn't concerned with these details.
Why?
The APR calculation uses for input the anticipated total payment amounts. Periodic interest never is used in the equation.
Also, the TILA creates rules for how to calculate an APR. All disclosures have to use the same equations. This is not true for interest calculations.
This is why the APR is a Very Important Number.
But the APR is not the only thing that Regulation Z requires the lender to disclose.
What disclosures does the TILA require?
The federal TruthinLending Act requires that borrowers receive written disclosures about important terms of credit before they are legally bound to pay the loan.
In addition to the APR, the following must be prominently shown:
Finance Charge: cost of credit expressed as a dollar amount (this is the total amount of interest and certain fees you will pay over the life of the loan if you make every payment when due);
Amount Financed: the dollar amount of credit provided to you;
Total of Payments: the sum of all the payments that you will have made at the end of the loan (this includes repayment of the principal amount of the loan plus all of the finance charges)
The TILA disclosure will also include other important terms of the loan such as the number of payments, the monthly payment, late fees, whether you can prepay your loan without a penalty, and other important conditions. Exactly what must be included on the disclosure statement varies depending on the conditions of the loan itself.
The disclosure statement that this calculator creates is fully compliant with the TILA.
Alright, we've defined "APR," and we've covered at a high level what loan terms must be disclosed, but how do I use the calculator?
That question gets answered in the next section.
Using the APR calculator
The annual percentage rate calculation, as Regulation Z documents it in Appendix J, does not care about pesky details.
The calculation does not need to know what the loan's compounding frequency is. It does not care if the loan uses 360 or 365 day years. It does not care if the interest is calculated using the same day months or calculated using the exact number of days in a month.
What the calculation requires is the following:
 The loan amount or amounts
 The payment schedule, meaning the loan's principal and interest payment amounts and when they are due. (These loan payments do NOT include any charges or fees.)
 The fees or charges the lender requires the borrower to pay.
Using these details, the calculator will calculate the four values lenders must reveal.
 Amount Financed
 Finance Charge
 Annual Percentage Rate
 Total of Payments
The amount financed is calculated by determining the principal loan amount and adding any other amounts that are financed by the creditor and are not part of the finance charge, and subtracting any prepaid finance charges such as prepaid interest and loan application fees.
The finance charge is the cost of consumer credit as a dollar amount. It includes any charge payable directly or indirectly by the consumer and imposed directly or indirectly by the creditor as an incident to or a condition of the extension of credit. Note, however, finance charges do not include any charge of a type payable in a comparable cash transaction.
Finance charges include but are not limited to the following (as quoted from 226.4 of Reg. Z):
 (1) Interest, time price differential, and any amount payable under an addon or discount system of additional charges.
 (2) Service, transaction, activity, and carrying charges, including any charge imposed on a checking or other transaction account to the extent that the charge exceeds the charge for a similar account without a credit feature.
 (3) Points, loan fees, assumption fees, finder’s fees, and similar charges.
 (4) Appraisal, investigation, and credit report fees.
 (5) Premiums or other charges for any guarantee or insurance protecting the creditor against the consumer’s default or other credit loss.
 (6) Charges imposed on a creditor by another person for purchasing or accepting a consumer’s obligation, if the consumer is required to pay the charges in cash, as an addition to the obligation, or as a deduction from the proceeds of the obligation.
 (7) Premiums or other charges for credit life, accident, health, or lossofincome insurance, written in connection with a credit transaction.
 (8) Premiums or other charges for insurance against loss of or damage to property, or against liability arising out of the ownership or use of property, written in connection with a credit transaction.
 (9) Discounts for the purpose of inducing payment by a means other than the use of credit.
 (10) Charges or premiums paid for debt cancellation or debt suspension coverage written in connection with a credit transaction, whether or not the coverage is insurance under applicable law.
Prepaid Interest
A special note about prepaid interest. Loans can and will close on any day of the month, not just on a payment due date. If payments are due on the first and a loan closes (loan amount is made available) on the twentysixth, the first payment frequently will not be due until the first of the 2nd month following the closing. That is, if the loan closes on July 26 the first payment will be due on September 1. The time between the loan closing and the first payment is longer than a month. This is called a long initial period. The lender is going to want the interest they are entitled to for these 6 days (July 26  August 1). They can collect the interest for the 6 days by adding it to the September 1 payment. Or, they can ask for the interest on the day the loan closes. If they collect it on the day the loan closes, this is prepaid interest.
You can use this interest calculator to calculate exact day prepaid interest.
But here's a tip. When it's all said and done, an APR disclosure statement is almost always just an estimate since it has to be given to the borrower even prior to the loan closing. Frequently the closing date isn't even known when the disclosure is provided. Therefore, keep it simple, and just assume regular length periods!
But with that said...
If the software used to calculate the APR is not accurate, the lender may be subject to fines and adverse publicity leading to reputational damage.
The next section will prove to you the accuracy of this calculator.
All the example from Regulation Z, Appendix J
Lenders and borrowers need to have confidence in the tools they use.
Is there any better way to prove the accuracy and flexibility of this calculator than to give the user the ability to quickly load each of the 20 calculations from Regulation Z, Appendix J, and allow them to calculate the results?
Of course not.
And that's just what this page does.
Click on the links below to preload the calculator with the inputs specified by the particular example. You can then click on "Calc" and compare the result with the result defined in the regulation.
Skeptical? Change one of the inputs and recalculate. You'll see the APR result change.
Not only does this confirm the accuracy of this calculator, but it also shows its flexibility. It handles even closedend loan examples with multiple loan advances such as construction loans and student loans. (I have not found another calculator on the web that can do these calculations.)
Go ahead, try a few examples. Remember, just click on a link and the details will be preloaded for you in the calculator. No need for manual entry!
The Examples
Regulation Z classifies the following five examples as "(1) Single advance transaction, with or without an odd first period, and otherwise regular."

Example (i): Monthly payment (regular first period)
 Amount advanced = $5,000. Payment = $230.
 Number of payment = 24.
 Loan advance 01/10/1978 First payment 02/10/1978.
 APR = 9.69%

Example (ii): Monthly payments (long first period)
 Amount advanced = $6,000. Payment = $200.
 Number of payments = 36.
 Loan advance 02/10/1978 First payment 04/01/1978
 APR = 11.82%

Example (iii): Semimonthly payments (short first period)
 Amount advanced = $5,000. Payment = $219.17.
 Number of payments = 24.
 Loan advance 02/23/1978. First payment 03/01/1978
 Payments made on 1st and 16th of each month.
 APR = 10.34%

Example (iv): Quarterly payments (long first period)
 Amount advanced = $10,000. Payment = 385.
 Number of payments = 40
 Loan advance = 05/23/1978. First payment = 10/01/1978
 APR = 8.97%

Example (v): Weekly payments (long first period)
 Amount advanced = $500. Payment = 17.60
 Number of payments = 30.
 Loan advance on 03/20/1978. First payment on 04/21/1978
 APR = 14.96%.
Regulation Z classifies the following two examples as "(2) Single advance transaction, with an odd first payment, with or without and odd first period, and otherwise regular."

Example (i): Monthly payments (regular first period and irregular first payment)
 Amount advanced = $5,000. First payment = $250. Regular payment = $230.
 Number of payments = 24.
 Loan advance on 01/10/1978. First payment on 02/10/1978
 APR = 10.08

Example (ii): Payments every 4 weeks (long first period and irregular first payment)
 Amount advanced = $400. First payment = $39.50
 Regular payment = $38.31. Number of payments = 12.
 Loan advance on 03/18/1978. First payment on 04/20/1978.
 APR = 28.50%
Regulation Z classifies the following two examples as "(3) Single advance transaction, with an odd final payment, with or without an odd first period, and otherwise regular."

Example (i): Monthly payments (regular first period and irregular final payment)
 Amount advanced = $5,000. Regular payment = $230.
 Final payment = $280. Number of payments = 24.
 Loan advance on 01/10/1978. First payment on 02/10/1978
 APR = 10.50%

Example (ii): Payments every 2 weeks (short first period and irregular final payment)
 Amount advanced = $200. Regular payment = $9.50.
 Final payment = $30. Number of payments = 20.
 Loan advance on 04/03/1978. First payment on 04/11/1978
 APR = 12.22%
Regulation Z classifies the following two examples as "(4) Single advance transaction, with an odd first payment, odd final payment, with or without an odd first period, and otherwise regular."

Example (i): Monthly payments (regular first period, irregular first payment, and irregular final payment)
 Amount advanced = $5,000. First payment = $250. Regular payment = $230.
 Final payment = $280. Number of payments = 24.
 Loan advance on 01/10/1978. First payment on 02/10/1978.
 APR = 10.90%

Example (ii): Payments every two months (short first period, irregular first payment, and irregular final payment)
 Amount advanced = $8,000. First payment = $449.36.
 Regular payment = $465. Final payment = $200. Number of payments = 20.
 Loan advance on 01/10/1978. First payment on 03/01/1978.
 APR = 7.30%
Regulation Z classifies the following four examples as "(5) Single advance, single payment transaction."

Example (i): Single advance, single payment (term of less than 1 year, measured in days)
 Amount advanced = $1,000. Payment = 1080.
 Loan advance on 01/03/1978. Payment on 09/15/1978.
 APR = 11.45%

Example (ii): Single advance, single payment (term of less than 1 year, measured in exact calendar months)
 Amount advanced = $1,000. Payment = $1044.
 Loan advance on 07/15/1978. Payment on 1/15/1979
 APR = 8.80%

Example (iii): Single advance, single payment (term of more than 1 year but less than 2 years, fraction measured in exact months)
 Amount advanced = $1,000. Payment = $1,135.19.
 Loan advance on 01/17/1978. Payment on 01/17/1980.
 APR = 8.76%

Example (iv): Single advance, single payment (term of exactly 2 years)
 Amount advanced = $1,000. Payment = $1,240.
 Loan advance on 01/03/1978. Payment on 01/03/1980.
 APR = 11.36%
Regulation Z classifies the following three examples as "(6) Complex single advance transaction."

Example (i): Skipped payment loan (payments every 4 weeks)
 Amount advanced = $2135. Payment = $100.
 Number of payments = 24. Payments are due every 4 weeks. However, in those months in which 2 payments would be due, only the first of the 2 payments is made and the following payment is delayed by 2 weeks to place it in the next month.
 Loan advance on 01/25/1978. First payment on 02/20/1978.
 APR = 12.00%

Example (ii): Skipped payment loan plus single payments
 Amount advanced = $7,350. Loan advance on 03/03/1978
 Payment = $1,000. Number of payments = 3. Payment on 09/15/1978.
 Payment = $2,000. Number of payments = 1. Payment on 03/15/1979.
 Payment = $750. Number of payments = 3. Payment on 09/15/1979.
 Payment = $1,000. Number of payments = 1. Payment on 02/01/1980.
 APR = 10.22%

Example (iii): Mortgage with varying monthly payments
 Amount advanced (net) = $39.688.56.
 Number of payments = 360.
 Loan advance on 04/10/1978. Payment on 06/01/1978.
 Payments are the same for 12 months at a time.

Year Monthly
PaymentYear Monthly
PaymentYear Monthly
Payment1 $291.81 11 $385.76 21 $380.43 2 300.18 12 385.42 22 379.60 3 308.78 13 385.03 23 378.68 4 317.61 14 384.62 24 377.69 5 326.65 15 384.17 25 376.60 6 335.92 16 383.67 26 375.42 7 345.42 17 383.13 27 374.13 8 355.15 18 382.54 28 372.72 9 365.12 19 381.90 29 371.18 10 375.33 20 381.20 30 369.50  APR = 9.80%
Regulation Z classifies the following two examples as "(7) Multiple advance transactions."

Example (i): Construction loan (3 loan advances followed by monthly payments)
 Amount advanced = $20,000 each.
 Loan advances on 04/10/1979, 06/12/1979, and 09/18/1979.
 Payment = $612.36. Number of payments = 240.
 Payment on 12/10/1979.
 APR = 10.25%

Example (ii): Student loan (8 loan advances, monthly payment, and the first payment before first advance)
 Payment = $240. Number of payments = 50. Payment on 07/01/1978.
 Amount advance = $1,800 on 09/05/78.
 Amount advance = $1,000 on 01/05/79.
 Amount advance = $1,800 on 09/05/79.
 Amount advance = $1,000 on 01/05/80.
 Amount advance = $1,800 on 09/05/80.
 Amount advance = $1,000 on 01/05/81.
 Amount advance = $1,800 on 09/05/81.
 Amount advance = $1,000 on 01/05/82.
 APR = 32.04%
Who must prepare a disclosure statement?
A lender, whether that lender is a business or an individual must comply with the TruthinLendingAct and provide the borrower with a disclosure statement prior to offering or extending credit when four conditions are met:
 The credit is offered or extended to consumers;
 The lender offers or extends credit regularly;
 The credit is subject to a finance charge or is payable by a written agreement in more than four installments; and
 The credit is primarily for personal, family, or household purposes.
Wrapping Up
As you can see, there is a lot to understanding the TruthInLending Act and an APR Disclosure Statement.
Norman T Roberts says:
How do you calculate APR for an interest only loan with points
Karl says:
I assume you see where to enter the points.
In the grid area of the calculator, you’ll have to create at least 3 rows. 1 loan amount row. I row showing the interest only payment amounts, and a third row for the payoff amount. If the payment amount changes at any point before the final payoff amount, then you would need to add additional rows anytime the payment changes.
The APR does not care about interest only per se. The APR calculation only cares about what the consumer pays.
If this isn’t clear, feel free to ask again.
sherry says:
Do you have a calculator for construction to permanent ARM mortgages where the payments were interest only in year 1?
Karl says:
This calculator will handle construction loans, ARMs and it supports interestonly payments, in the first year, or for any year along with the regular principal and interest payments.
Scroll down the page for tutorials.
Please ask if you have any questions.
Vik says:
I am using example 8. Example (i): Monthly payments (regular first period and irregular final payment).
Is it possible to recreate the calculation in Excel? If so, what wold the formula look like?
Thank you!
Karl says:
There are two questions here. I don’t know Excel programming, so I can’t answer your question if you can recreate it in Excel. As to the formula, get a hold of a copy of the TruthinLending Act (I think I have a link to on the page as I recall). The math is included in the Reg.
Russ Tolleson says:
I am looking for a calculator that will handle ARM loans by accomplishing the following calculations:
Handle a fixed interest period before becoming adjustable (such as a 5/1 or 5/6).
Be able to recalculate the new interest rate and monthly payment at the end of the fixed period and at each rate change period based on the assumption the maximum interest rate change allowed (based on starting rate, margin, caps) at that change period.
Continue the calculation until the maximum interest rate is reached and then amortize out the loan.
Karl says:
My mistake in the last reply. I thought your comment was on a different calculator page.
Please see this adjustable rate calculator page.
It will create an amortization schedule that lets the user change the rate to any interest rate between 99% and 99% on any date. But the user needs to know the rules as to when the rate can change and what the maximum rate is.