How It Works

NPER calculates the number of periods needed to pay off a loan. By comparing the standard payoff time to payoff with extra payments, you can see exactly how much time (and money) you’ll save.

Syntax

=NPER(rate, payment, present_value)

rate: Monthly interest rate (annual ÷ 12)
payment: Monthly payment amount (negative)
present_value: Current loan balance

Example

Your Situation:

Credit Card Balance: $8,000
Interest Rate: 22% APR
Minimum Payment: $200/month
Extra Payment: $100/month

Time to Pay Off (Minimum Only):

=NPER(22%/12, -200, 8000)

Result: 62 months (5+ years)

Time with Extra $100:

=NPER(22%/12, -300, 8000)

Result: 33 months (under 3 years)

Months Saved: 29 months!

Calculating Interest Savings

Total Interest Without Extra

=payment * NPER(rate/12, -payment, balance) - balance

Total Interest With Extra

=(payment + extra) * NPER(rate/12, -(payment + extra), balance) - balance

Interest Saved

=interest_without - interest_with

Complete Analysis Table

Scenario	Formula	Result
Months (min only)	`=NPER(22%/12, -200, 8000)`	62
Months (+$100)	`=NPER(22%/12, -300, 8000)`	33
Months saved	`=B2-B3`	29
Total paid (min)	`=200*B2`	$12,400
Total paid (+$100)	`=300*B3`	$9,900
Interest (min)	`=B5-8000`	$4,400
Interest (+$100)	`=B6-8000`	$1,900
Interest saved	`=B7-B8`	$2,500

That extra $100/month saves you $2,500 in interest!

Finding the Optimal Extra Payment

Pay Off in Specific Time

Want to be debt-free in 24 months?

=PMT(rate/12, 24, balance) * -1 - current_payment

This tells you how much extra you need.

Double Your Payment Impact

Every dollar extra goes straight to principal. At 22% APR, $100 extra saves roughly $22/year in interest - a 22% return!

Comparing Debts

Which debt benefits most from extra payments?

Debt	Balance	Rate	$100 Extra Saves
Credit Card	$5,000	22%	$1,847
Car Loan	$15,000	7%	$892
Student Loan	$25,000	5%	$1,156

Formula for interest saved:

=PMT(rate/12, NPER(rate/12, -payment, balance), balance) * NPER(rate/12, -payment, balance) - balance - (PMT(rate/12, NPER(rate/12, -(payment+100), balance), balance) * NPER(rate/12, -(payment+100), balance) - balance)

Higher interest rates benefit more from extra payments (mathematically). But psychology matters too - see debt snowball method.

Pro Tips

Even $25 helps - small consistent extra payments add up significantly
Specify “principal only” - tell your lender extra payments should go to principal, not future payments
Windfalls matter - tax refund or bonus applied to debt has huge impact
Biweekly payments - paying half your payment every 2 weeks = 13 full payments per year (one extra)

Biweekly Payment Calculator

=NPER(rate/26, -(payment/2), balance)

Divide by 26 for biweekly periods. This alone can cut years off a mortgage.

Common Errors

#NUM! error: Payment too small to ever pay off the debt - increase payment amount
Negative result: Your extra payment is larger than needed - debt would be paid off immediately

Extra Payment Impact