HP 12C Learn

Mortgage Payment (PMT) Step by Step

Calculate a monthly mortgage payment with a clean PV, i, n, and PMT workflow on the HP 12C.

7 min

What this solves

This tutorial shows how to compute a monthly mortgage payment from loan amount, interest rate, and term.

Before you start

  • Clear the financial registers before entering a new loan problem.
  • Make sure the interest rate and the number of periods use the same time unit.
  • Decide whether the problem is END mode or BEGIN mode.

Key ideas

TVM entry order is flexible

You can enter n, i, PV, PMT, and FV in the order that feels natural.

Sign convention matters

If PV is money received, PMT should come back as money paid.

Worked example 1

Example: monthly payment for a fixed-rate mortgage

Estimate the monthly payment on a 30-year mortgage with a known principal and annual rate.

Setup

  • Use END mode for a standard end-of-month payment.
  • Assume the loan amortizes fully, so FV is zero.

Inputs

Loan amount (PV)
250,000
Annual rate
6.00%
Term
360 months
Future value (FV)
0

Keystrokes and checkpoints

1
f CLEAR REG
Reset the financial state.
Display: 0.00
2
g END
Select end-of-period payments before solving. The BEGIN indicator should be off.
3
360 n
Store the number of monthly periods.
Display: 360.00
4
6 g 12÷
Convert the annual nominal rate to a monthly rate and store it in i. Do not press i again.
Display: 0.50
5
250000 PV
Enter the principal as present value.
Display: 250,000.00
6
0 FV
Set the final balance to zero.
Display: 0.00
7
PMT
Solve for the monthly payment.
Display: -1,498.88

Result

The monthly payment is about -1,498.88 for a 250,000 loan at 6% nominal annual interest over 360 months.

Interpretation

The negative sign means money paid out when PV was entered as money received.

Sanity checks

  • If the payment is positive, your sign convention is probably wrong.
  • If the answer is absurd, check whether annual and monthly units were mixed.
  • If the problem should be BEGIN mode, the answer must change.

Why it works

  • TVM keys solve the time-value relationship once the period assumptions match.
  • The negative PMT is expected and follows cash-flow sign convention.
  • Most mortgage workflows become repeatable once n and i share the same period.

Common mistakes

  • Entering annual periods with monthly payments.
  • Using the wrong sign convention for PV and PMT.
  • Forgetting that BEGIN mode changes the answer.
  • Typing the annual rate as if it were already monthly.

Practice prompt

Run the same example twice, once in END mode and once in BEGIN mode, and compare the payment result.

Try it in the HP 12C emulator

Follow the steps above, then test the sequence live.

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