Extra Payment Calculator
What an extra monthly payment does: months shaved off and interest saved.
The fastest way to shorten a loan is an extra payment every month. This calculator shows exactly how many months an extra amount takes off your debt and how much interest it saves.
At a glance
- What you enter
- Current balance, Annual interest rate, Current monthly payment, Extra per month
- What you get
- Months with extra payments, Interest saved, Months shaved off
- Formula shown
- Yes — every step, right below your results.
- Cost and privacy
- Free, no account needed, and nothing you type is stored.
See worked examples ↓ Read the FAQ ↓ Share this calculator ↓
Results are estimates for general information only — always verify with a professional or official source before acting on them.
How to use the Extra Payment Calculator
- 1 Enter Current balance
- 2 Enter Annual interest rate
- 3 Enter Current monthly payment
- 4 Enter Extra per month
- 5 Press Calculate. You get Months with extra payments, Interest saved, Months shaved off, and every intermediate step stays visible under “How is this calculated?”
- 6 Change one number at a time to see what moves the result — that is usually the most useful thing a calculator can tell you.
Worked examples
Real numbers run through this calculator. Open any example to load it into the form above and change it.
$10,000 at 6%, paying $300 plus $100 extra
A cheaper loan with a modest top-up.
You enter
- Current balance
- $10,000.00
- Annual interest rate
- 6%
- Current monthly payment
- $300.00
- Extra per month
- $100.00
You get
- Months with extra payments
- 27
- Interest saved
- $257.42
- Months shaved off
- 10
The extra $100 a month — a third more than the current payment — finishes the loan in about 27 months instead of 37, and saves roughly $257 in interest.
$6,000 at 22%, where $150 barely covers the interest
A high-rate balance doubled from $150 to $300 a month.
You enter
- Current balance
- $6,000.00
- Annual interest rate
- 22%
- Current monthly payment
- $150.00
- Extra per month
- $150.00
You get
- Months with extra payments
- 25
- Interest saved
- $3,370.66
- Months shaved off
- 48
At 22% the balance adds $110 of interest a month, so the $150 plan drags on for about 73 months and costs close to $4,913 in interest. Doubling the payment clears it in about 25 months and saves roughly $3,371 — the same $150 buys far more when it goes to the balance instead of the interest.
Guides that go with it
How to Get Out of Debt: A Step-by-Step Guide for Beginners
Debt feels like a room with no doors. You pay and pay, and the balance barely moves. By the end of this guide you will have a written list of every debt you owe, a payoff order that actually makes sen…
How to Save $1,000 When You Don't Think You Have Extra Money
A thousand dollars sounds like a number for people who already have money. It isn't. It's roughly $38 a week for six months, or about $2.75 a day. That's a coffee, a bus fare you didn't take, one forg…
How to Save Money for a Big Purchase Without Going Into Debt
By the end of this guide you will have a working savings plan for one specific big purchase: a target amount, a deadline, a monthly number, and a place to keep the money so you are not tempted to spen…
Frequently asked questions
Will my lender apply the extra money to the balance?
Usually, but the mechanics differ and they matter. Some lenders apply extra amounts to principal automatically and shorten the term, some hold them as a prepayment for next month, and some charge a fee for overpaying. Ask which applies to your account before you commit to a monthly extra, and check the first statement afterwards to confirm the balance fell by more than the scheduled amount.
Why does a small extra payment save so much interest?
Because of how amortisation works: in the early months most of your payment is interest, so the balance barely moves. An extra payment goes straight onto the balance, and every dollar removed stops accruing interest for the whole remaining term — that compounding is what turns $100 a month into hundreds saved. The effect shrinks the later you start, which is why the same extra is worth most at the beginning.
Does the calculator assume the extra amount every single month?
Yes — the new plan adds that amount to every payment until the balance reaches zero, so a payment you can only manage twice a year should not be entered as a monthly extra. For a one-off lump sum, subtract it from the balance yourself and run the reduced figure through the Debt Payoff Calculator instead, or enter the monthly equivalent if you would rather build it up gradually.
What if my current payment is already lower than the monthly interest?
Then the “months at the current payment” line is a placeholder, because the balance never falls, and the months-saved comparison has no meaning. Fix the starting point first: raise the current payment until it clears the interest with something left over, which the Minimum Payment Calculator shows as the “goes toward the balance” line. Only then is the extra-payment comparison worth reading.
Terms used here
Short, plain-language definitions of the words this calculator uses.