BedrockCalc — bedrockcalc.com
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Payment Calculator
Some people know the term and need the payment; others know what they can pay and need the timeline. This loan payment calculator solves both directions — monthly payment from a term, or payoff time from a fixed payment.
See how this works on a $25,000 loan at 7% — 3 real examples
Monthly payment
$0
Loan term
—
Total interest
$0
Total of payments
$0
One payment, month by month
- Interest—
- Principal—
Loan balance over time
Amortization scheduleMonth-by-month breakdown
How this loan payment calculator solves both directions
Both modes use the same fixed-rate amortization relationship, just rearranged for the unknown:
Solve payment: M = P · r(1 + r)n / ((1 + r)n − 1)
Solve time: n = −log(1 − P·r / M) / log(1 + r)
r = annual rate / 12 P = loan amount M = monthly payment
In Solve payment mode the calculator amortizes the loan amount over your chosen term and returns the level monthly payment M; total of payments is M × n and total interest is that total minus the loan amount. In Solve time mode it inverts the same formula to find the number of months n a fixed payment takes to clear the balance — the final period is partial, so a fractional month is normal. If the payment does not exceed the first month’s interest (P × r) the balance can never fall, so instead of an impossible answer the calculator shows a warning to raise the payment. Assumptions: the rate is fixed for the whole loan, payments are monthly, the first payment lands one month from today, and no fees, insurance or taxes are added — enter those separately if your loan has them.
Name the term, or name the payment
The same $25,000 at 7%, approached from both ends — and one payment that technically works but barely does.
Known term: five years to zero
per month$495.03
- Spreading $25,000 over sixty payments prices each one at $495.03.
- Interest across the five years comes to $4,702.
- The schedule is the contract: sixty payments, then a zero balance, no surprises.
When the deadline is fixed, the calculator hands you the payment that meets it.
Load this example (opens in a new tab)Known payment: $750 a month
to payoff38 months
- A $750 payment retires the loan in 38 months — three years and two months.
- Interest falls to $2,881, which is $1,821 under the five-year plan.
- The last payment is smaller than the rest; the balance simply runs out.
Choosing the payment first turns the term into the output instead of the input.
Load this example (opens in a new tab)The payment that barely qualifies
to payoff51+ years
- Interest on $25,000 at 7% runs about $146 a month; a $150 payment clears about $4 of debt.
- The loan technically ends — after 617 months, fifty-one years and five months.
- Total interest reaches $67,416, well over twice the amount borrowed.
A payment can be big enough to be accepted and still too small to be useful.
Load this example (opens in a new tab)Illustrations only, not financial advice. Your own rate, taxes and insurance will differ — check with a qualified financial advisor before acting on any of this.
Loan payments and payoff time, in plain English
- Two questions, one tool. Use “Solve payment” when you know the term and want the monthly loan payment; use “Solve time” when you know what you can pay and want to know how long to pay off the loan.
- Longer term, smaller payment, more interest. Dropping a payment by stretching the term always increases the total interest — the calculator shows both so the trade-off is visible.
- Every extra dollar attacks principal. In “Solve time” mode a payment even slightly above the required amount can shave months off, because interest is charged only on the shrinking balance.
- Watch the interest floor. A payment at or below the first month’s interest never retires the balance — a common trap on high-rate revolving debt.
- Fixed-rate, monthly only. This is a simple loan payment calculator for fixed-rate installment loans; variable rates, fees and taxes need their own adjustments.
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Frequently asked questions
How do I find my monthly loan payment?
Switch this loan payment calculator to “Solve payment,” enter the loan amount, interest rate and term, and it returns the level monthly payment from the standard amortization formula. For example, $25,000 at 7% over 5 years comes to $495.03 a month — $29,701.89 paid in total, of which $4,701.89 is interest.
How long will it take to pay off a loan at a fixed monthly payment?
Choose “Solve time,” enter the balance, rate and the amount you can pay each month, and this how-long-to-pay-off-a-loan calculator returns the number of months. Paying $495 a month on that same $25,000 balance at 7% clears it in about 60 months; paying more shortens it sharply because extra dollars go straight to principal.
What happens if my payment does not cover the interest?
The balance grows instead of shrinking, so the loan is never repaid. At 7% on a $25,000 balance the first month alone accrues $145.83 of interest, so any payment at or below that only treads water. When that happens the calculator flags it and asks you to raise the payment rather than showing an impossible payoff date.
How is total interest calculated?
Total interest is simply the total of every payment minus the original loan amount. Because interest is charged on the outstanding balance each month, a longer term means more months of interest even at the same rate — which is why total interest can climb even as the monthly payment falls.
Does a longer term lower my monthly payment?
Yes, but at a cost. Stretching that $25,000 7% loan from 5 years to 6 years drops the monthly payment from about $495 to roughly $426, but total interest rises from about $4,702 to about $5,690. A shorter term costs more each month and far less overall.
Is this a simple loan payment calculator I can use for any loan?
Yes. It is a simple loan payment calculator for any fixed-rate installment loan — personal, auto, student, home-equity or a general note — as long as the rate is fixed and payments are monthly. Enter your own numbers; nothing is loan-type specific and no fees or taxes are assumed.
Disclaimer: these calculators are educational tools, not financial advice. They model your inputs with published formulas, but they cannot know your full situation — for decisions with real stakes, talk to a qualified professional. Formulas and defaults last reviewed .