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HP 12C Online Calculator

By Bruno Tonetto · Reviewed on · How we verify

The HP-12C is the classic financial calculator, famous for its RPN notation (there is no = key). This free HP 12C online calculator emulates the original — keyboard, display and RPN stack — and solves loans, future value, present value and interest rate conversions right in your browser. Launched in 1981 and still in production, the 12C remains a fixture of finance and real-estate courses, and it is one of only two calculator models allowed in the CFA exams ↗.

How to use the HP 12C online

The HP-12C uses RPN (Reverse Polish Notation): instead of typing 2 + 3 =, you enter the numbers before the operator. There is no = key. To add 2 + 3:

2 ŷ,r PREFIX ENTER LSTx 3 n! → the display shows 5.

PREFIX ENTER LSTx pushes the first number onto the stack; the second goes into the display; the operator combines the two. For 9 ÷ 2 + 3: 9 MEM PREFIX ENTER LSTx 2 ŷ,r 3 n! .

The financial keys

Five registers solve the classic compound-interest problems (END mode, with payments at the end of each period):

How it works: type the number and tap the key to store it. Once 4 of the 5 are set, tap the remaining key and the HP computes it automatically. The display indicator shows which registers already hold a value.

Sign convention: money coming in is positive, money going out is negative. In a loan, PV is positive (you received the cash) and PMT comes out negative; in savings, PMT is negative (you are putting money in) and FV comes back positive. Use CHS DATE to flip the sign.

The display follows the original HP convention — decimal point and thousands comma — which happens to match everyday American notation: 1,234.56 reads the same on the machine and on your bank statement.

The orange (f) and blue (g) functions

Almost every key carries extra functions printed in orange (prefix f ) and blue (prefix g ). Press the prefix and then the key where the function is printed. Factorial (n!), for example, is in blue on the 3 n! key. So 5! is:

5 M.DY g 3 n!

Result: 120.

Other blue-prefix functions: square root g PRICE yˣ √x (√x), natural log g SL %T LN (LN), exponential g YTM 1/x eˣ (eˣ), fractional part g SOYD Δ% FRAC (FRAC) and integer part g DB % INTG (INTG). The emulator also covers statistics ( Σ+ Σ− , g 0 x̄ for the mean, g . s for standard deviation), depreciation, cash flow (NPV and IRR) and dates.

Step-by-step examples

1. Future value of monthly savings (FV)

How much do you end up with saving $500 a month at 0.4% a month (about 4.9% a year) for 360 months (30 years)?

. s 4 D.MY INT i 12÷ 3 n! 6 x̄w 0 x̄ AMORT n 12× 5 M.DY 0 x̄ 0 x̄ CHS DATE RND PMT CFj IRR FV Nj

Result: 401,073.74 — about $400,000, of which only $180,000 came out of your pocket. CHS makes the PMT negative (money going out), so FV comes back positive (what you accumulate).

2. Present value of a payment plan (PV)

A purchase paid in 12 installments of $200: what is the equivalent cash price (the present value of the payments) if your money earns 0.4% a month?

. s 4 D.MY INT i 12÷ 1 x̂,r 2 ŷ,r AMORT n 12× 2 ŷ,r 0 x̄ 0 x̄ CHS DATE RND PMT CFj NPV PV CFo

Result: 2,338.75. The payments go out (CHS, negative), so PV comes back positive: any cash price below that is the better deal.

3. The monthly payment on a loan (PMT)

What is the monthly payment on a $30,000 car loan over 60 months at 7% APR? The 12C wants the rate per month, so divide the APR by 12 right on the stack:

7 BEG PREFIX ENTER LSTx 1 x̂,r 2 ŷ,r INT i 12÷ 6 x̄w 0 x̄ AMORT n 12× 3 n! 0 x̄ 0 x̄ 0 x̄ 0 x̄ NPV PV CFo RND PMT CFj

Result: −594.04. The minus sign means the payment leaves your pocket. That is 60 payments of $594.04.

4. The implied interest rate (i)

A $30,000 loan repaid in 60 payments of $594.04 (the payment from example 3): what rate is it charging?

f 4 D.MY 6 x̄w 0 x̄ AMORT n 12× 5 M.DY 9 MEM 4 D.MY . s 0 x̄ 4 D.MY CHS DATE RND PMT CFj 3 n! 0 x̄ 0 x̄ 0 x̄ 0 x̄ NPV PV CFo INT i 12÷

Result: 0.5834 — about 0.58% a month; times 12, you are back at the 7% APR. The opening f 4 D.MY sets 4 decimal places so the rate is visible in full.

5. Number of payments (n)

How many payments of $594.04 (at 7% APR) does it take to pay off $30,000?

7 BEG PREFIX ENTER LSTx 1 x̂,r 2 ŷ,r INT i 12÷ 5 M.DY 9 MEM 4 D.MY . s 0 x̄ 4 D.MY CHS DATE RND PMT CFj 3 n! 0 x̄ 0 x̄ 0 x̄ 0 x̄ NPV PV CFo AMORT n 12×

Result: 60 (the display shows 60.00) — 60 payments. On the physical HP-12C, n always comes out as a whole number, rounded up.

6. Annual rate to monthly (pure RPN)

Turning 7% a year (compound) into the equivalent monthly rate: (1 + 7%)1/12 − 1.

f 4 D.MY 1 x̂,r PREFIX ENTER LSTx 7 BEG DB % INTG 1 x̂,r 2 ŷ,r YTM 1/x eˣ PRICE yˣ √x 1 x̂,r

Result: 0.0057, i.e. about 0.5654% a month. The opening f 4 D.MY sets the display to 4 decimals (with 2 you would only see 0.01).

Note: that is the equivalent rate, with compounding — the right way to compare investments. US loan contracts instead divide the APR by 12 (7% → 0.5833% a month, as in example 3); the two conventions give slightly different numbers.

7. Monthly rate to annual (pure RPN)

The reverse trip — 0.5654% a month to the equivalent annual rate: (1 + 0.5654%)12 − 1.

f 4 D.MY 1 x̂,r PREFIX ENTER LSTx . s 5 M.DY 6 x̄w 5 M.DY 4 D.MY DB % INTG 1 x̂,r 2 ŷ,r PRICE yˣ √x 1 x̂,r

Result: 0.0700 — back to the 7% a year of the previous example.

In Excel or Google Sheets

The HP-12C keys map directly to the spreadsheet financial functions:

HP-12C → Excel / Google Sheets:

RND PMT CFj =PMT(i, n, PV, FV)
IRR FV Nj =FV(i, n, PMT, PV)
NPV PV CFo =PV(i, n, PMT, FV)
INT i 12÷ =RATE(n, PMT, PV, FV)
AMORT n 12× =NPER(i, PMT, PV, FV)

Keep the same sign convention (money going out is negative), just like on the HP-12C. The cash-flow keys f NPV and f IRR correspond to NPV and IRR. Working with Excel in Spanish or Portuguese? Every one of these functions has a different name there — see the Excel function translator.

Frequently asked questions

Why is there no equals key on the HP 12C?

Because it uses RPN: the result appears the moment you press the operator, no = needed. That removes parentheses entirely and speeds up chained calculations.

My result came out negative — is that wrong?

No. The minus sign is the cash-flow convention: it marks money going out. A loan payment leaves your pocket, so it shows up negative.

How do I change the number of decimal places?

Press f followed by the number of places. For example, f 4 shows four decimals.

Does it work on my phone?

Yes. This HP 12C online calculator is responsive — just tap the keys. On a computer you can also type: numbers, + − × ÷, Enter, C, H and the initials N I P M V for the financial keys.

Which functions are implemented?

Beyond TVM (n, i, PV, PMT, FV) and RPN arithmetic: powers and logarithms (yˣ, √x, eˣ, LN, 1/x), %, %T, Δ%, n! (factorial), FRAC/INTG, RND, simple interest (INT), amortization (AMORT), cash flow (NPV and IRR), depreciation (SL, SOYD, DB), statistics with linear regression (Σ+, x̄, s, x̄w, x̂, ŷ) and dates (ΔDYS, DATE). What it does not include is step programming.

How is it different from the physical HP 12C?

The calculation engine is the same (compound interest in END mode) and the RPN stack behaves identically. This emulator covers practically every everyday function; it only leaves out the step programming (P/R, R/S, GTO) of the physical unit.

The emulator reproduces the HP-12C's math. For a real contract, confirm amounts and fees with your lender.

HP-12C and HP are trademarks of HP Inc. This is an independent educational emulator, not affiliated with or endorsed by HP.