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Loan affordability calculator

Find how much you can borrow from the monthly payment you can afford at your rate and term, and the price your down payment then buys.

Updated Checked against 4 worked examples

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%
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Try
Loan you can afford
$
Loan you can afford: $186,198.20
Shown to 2 decimal places, half-even
Price with your down payment
$236,198.20
Total of payments
$360,000.00
Total interest
$173,801.80
Number of payments
240
Lenders also cap payments by income (debt-to-income ratio) and add fees; treat this as the upper limit your budget allows.

A payment of $1,500.00 a month for 240 months supports a loan of $186,198.20; with your down payment that buys up to $236,198.20. Of the $360,000.00 you pay in total, $173,801.80 is interest.

What your payments cover

$186.2Kloan
Principal51.7%Interest48.3%

Loan you can afford at other rates

$0$100K$200K$300K0%5%10%15%Interest rate (per year)7.5%
Repayment schedule for this loan (240 rows)
MonthPaymentPrincipalInterestBalance
1$1,500.00$336.26$1,163.74$185,861.94
2$1,500.00$338.36$1,161.64$185,523.57
3$1,500.00$340.48$1,159.52$185,183.09
4$1,500.00$342.61$1,157.39$184,840.49
5$1,500.00$344.75$1,155.25$184,495.74
6$1,500.00$346.90$1,153.10$184,148.84
7$1,500.00$349.07$1,150.93$183,799.77
8$1,500.00$351.25$1,148.75$183,448.52
9$1,500.00$353.45$1,146.55$183,095.07
10$1,500.00$355.66$1,144.34$182,739.42
11$1,500.00$357.88$1,142.12$182,381.54
12$1,500.00$360.12$1,139.88$182,021.42
How it's calculated S
  1. Monthly rate and number of payments

    r=7.51200=0.00625,n=240r = \frac{7.5}{1200} = 0.00625,\qquad n = 240
  2. Present value of your payments

    P=1,500.00×1−(1+0.00625)−2400.00625=186,198.20P = 1{,}500.00 \times \frac{1 - (1 + 0.00625)^{-240}}{0.00625} = 186{,}198.20

    This is the EMI formula solved for the loan amount.

  3. Price with your down payment

    186,198.20+50,000.00=236,198.20186{,}198.20 + 50{,}000.00 = 236{,}198.20

About the loan affordability calculator

This works the EMI formula backwards. Given the monthly payment you can afford, the largest loan it repays is P = M × (1 − (1 + r)^−n) ÷ r, where r is the monthly rate and n the number of payments; this is what Excel's PV function returns. Adding your down payment gives the highest price you can pay.

With the defaults, 1,500 a month for 20 years at 7.5% supports a loan of 186,198.20, and 50,000 down lifts the price you can afford to 236,198.20. The 240 payments total 360,000.00, of which 173,801.80 is interest.

The result is the ceiling your budget sets. Lenders also limit the payment by your income through the debt-to-income ratio, and property tax, insurance and fees come out of the same monthly budget.

Worked examples

500 a month for 20 years at 8%

Monthly payment you can afford
500
Interest rate (per year)
8%
Tenure
20
Tenure in
Years
Down payment you have
0
Loan you can afford
59,777.15
Total interest
60,222.85

Checked against: Microsoft PV function documentation example: PV(0.08/12, 12*20, 500) = −59,777.15

1,500 a month for 20 years at 7.5% with 50k down

Monthly payment you can afford
1500
Interest rate (per year)
7.5%
Tenure
20
Tenure in
Years
Down payment you have
50,000
Loan you can afford
186,198.20
Price with your down payment
236,198.20

Checked against: Python decimal (prec 50) present value of an ordinary annuity

Zero rate

Monthly payment you can afford
1000
Interest rate (per year)
0%
Tenure
12
Tenure in
Months
Down payment you have
0
Loan you can afford
12,000.00
Total interest
0.00

Checked against: M × n when there is no interest

One month at 12%

Monthly payment you can afford
1010
Interest rate (per year)
12%
Tenure
1
Tenure in
Months
Down payment you have
0
Loan you can afford
1,000.00
Total interest
10.00

Checked against: 1010 / 1.01 by hand

Questions

How much can I borrow with a given monthly payment?

Multiply the payment by the annuity factor (1 − (1 + r)^−n) ÷ r. At 8% over 20 years, r = 0.08 ÷ 12 and n = 240, so the factor is 119.55 and a payment of 500 a month supports a loan of 59,777.15. Microsoft's documentation for Excel's PV function gives the same figure for PV(0.08/12, 240, 500).

What debt-to-income ratio do lenders accept?

In the US, the CFPB suggests keeping total debt payments at 36% of gross monthly income or less and housing costs at 28% to 35%, though some lenders go to 43% or higher. Fannie Mae's standard maximum is 36%, rising to 45% with credit-score and reserve requirements and to 50% for loans underwritten through Desktop Underwriter. On a gross income of 5,000 a month, 36% is 1,800.

How does the interest rate change how much I can borrow?

A higher rate means more of each payment goes to interest, so the same payment supports a smaller loan. Over 20 years, 1,500 a month supports 201,187.51 at 6.5%, 186,198.20 at 7.5% and 172,846.26 at 8.5%: each percentage point costs about 7% of the loan. The chart shows the full curve for your payment and term.

Does a longer loan term let me borrow more?

Yes, but with diminishing returns and much more interest. At 7.5%, 1,500 a month supports 161,810.14 over 15 years, 186,198.20 over 20 years and 214,526.44 over 30 years. Going from 20 to 30 years adds 28,328.24 of borrowing but raises total interest from 173,801.80 to 325,473.56.

How accurate is the loan affordability calculator?

Accuracy depends on your inputs and the method's assumptions. Decimal arithmetic uses 50 significant digits, but estimates, numerical methods and source data can be less precise; the displayed rounding does not remove those limits. It is checked against 4 worked examples whose answers come from independent sources; for example, “500 a month for 20 years at 8%” is checked against Microsoft PV function documentation example: PV(0.08/12, 12*20, 500) = −59,777.15.

Where does the method come from?

Microsoft Excel PV function; Consumer Financial Protection Bureau — Debt-to-income ratio.

About this calculator

P=M⋅1−(1+r)−nr,r=annual rate1200P = M \cdot \frac{1 - (1+r)^{-n}}{r},\qquad r = \frac{\text{annual rate}}{1200}

Sources

  1. Microsoft Excel PV function
  2. Consumer Financial Protection Bureau — Debt-to-income ratio

For planning only. Lenders, tax authorities and markets apply their own rounding, fees and rules; confirm figures with them before you commit.

Checked against references

4 worked examples with independently sourced answers ship with this calculator. They run in the test suite; you can run them here too.

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