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| Draft
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
2
360 n
Store the number of monthly periods.
Display: 360
3
6 g 12÷ i
Convert the annual nominal rate to a monthly rate and store it.
Display: 0.5
4
250000 PV
Enter the principal as present value.
Display: 250000
5
0 FV
Set the final balance to zero.
Display: 0
6
PMT
Solve for the monthly payment.
Display: Negative payment
Result
The HP 12C should return a negative monthly payment.
Interpretation
The sign should be negative if 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.