Financial keys with cash-flow signs
Money in is positive, money out is negative. Choose the key you want to solve.
The financial keys and the fields
A handheld financial calculator solves the same equation as the financial calculator here, but it asks for signs. Each key stores one number, and the fifth comes out of the math.
| Key | Field | What to enter |
|---|---|---|
| n | n | Number of periods (months, for a monthly rate) |
| i | i | Rate per period, in percent (1 for 1%) |
| PV | PV | Present value, with a sign |
| PMT | PMT | Payment each period, with a sign |
| FV | FV | Future value, with a sign |
| CHS | Sign | Flips positive and negative |
| g BEG, g END | Mode | Payment at the start or the end of the period |
On the real calculator, the n and i keys have a second function that saves typing: g 12× on the n key turns years into months, and g 12÷ on the i key turns a yearly rate into a monthly one.
Step by step: a $10,000 loan
- Type 12 and press n.
- Type 1 and press i.
- Type 10,000 and press PV. You receive the money, so it stays positive.
- Keep FV at 0, since the loan is paid off at the end.
- Press PMT. The display shows −888.49, the payment, which is money going out.
On this page, leave "Key to solve" on PMT and use the default values. Switch the mode to BEG, and the payment becomes −879.69.
Mortgage-style example: a $300,000 loan at 6.5% a year for 30 years. Press 30 g n (360), 6.5 g i (0.5417), 300,000 PV, then PMT. The display shows −1,896.20. The rate is only an example.
Signs and the most common errors
- Sign error: PV and PMT with the same sign (both positive) have no solution, because money never goes both in and out. This is the most common cause of an error on a financial calculator.
- Rate as a fraction: type 1 for 1%, not 0.01.
- Wrong mode: a regular loan uses END. Rent paid in advance uses BEG. A leftover BEG from an earlier problem is a classic mistake.
- Yearly rate with monthly payments: divide the yearly rate by 12 first, or use g 12÷.
| Situation | PV | PMT | FV |
|---|---|---|---|
| Loan | + (you receive) | − (you pay) | 0 |
| Savings with deposits | − (you put in) | − (you deposit) | + (you withdraw) |
| One lump sum | − (you put in) | 0 | + (you withdraw) |
Back to the calculator
Main calculatorFinancial calculatorN, I/Y, PV, PMT, and FV: enter four, solve for the fifthFrequently asked questions
How do I calculate a loan payment on an HP-12C?
Enter the number of payments in n, the rate per period in i, and the loan in PV, then press PMT. For $10,000, 12 months, and 1% a month, the display shows −888.49.
Why does the HP-12C show a negative payment?
The payment is money going out. The calculator uses positive for cash in and negative for cash out.
How do I put the HP-12C in BEG mode?
Press g, then the 7 key (BEG). The display shows BEGIN. To go back to END, press g and the 8 key.
What does Error 5 mean on a financial calculator?
Error 5 means the values cannot be solved, usually because of the signs on PV, PMT, and FV. Use CHS to flip one of them so there is both a cash in and a cash out.
Is there a free online HP-12C style calculator?
Yes. This page works in your browser and needs no download. For a version without signs, with Loan and Savings tabs, see the financial calculator.
Sources and review
- Financial mathematics: formulas for equal payments (annuities) with compound interest.