Amortizing Loan...Does This Automatically Mean Interest Accrual is 30/360?

I'm trying to model an amortizing loan, pretty plain vanilla. Assuming you have a 10 year loan on a 30 year amortization period, does this automatically mean interest accrual method must be 30/360? 

I've seen some lenders quote actual/360, or perhaps actual/365, but those were for interest only loans. 

Is it right to assume that if a loan is amortizing, the interest accrual method is 30/360? I guess maybe you can switch to an actual/360 in the PMT function, but that would be messy and the payments would change from month to month?

4 Comments
 
Most Helpful

Not sure I ever looked at load docs that closely with regard to interest calcs, but at least for partial payoff months (and first month) a daily interest calc is needed and I'd presume it specified in the doc (or its method calculation)

That said... for excel... when you use formulas like PV, PMT, RATE, NPER.... they have no concept or knowledge of days/months/years.... If you specify NPER in months (like 360 for 30 years), then divided the interest rate by 12 (standard method)... it is making a "pmt" of 360 periods.... those could be days, months, years, decades.... you just know and interpret it as months. 

Everytime I've used PMT as above for mortgage calcs, it came back with the monthly payment as stated by the lender, so, I'd guess the works. For daily interest charges (like for a payoff), I kinda think I have seen rate/365, but can't remember, the difference vs. 360 is probably never been enough to worry about! 

 

No, an amortizing loan does not always imply 30/360 interest accrual. 30/360 & actual/360 are just ways to determine what portion of the fixed payment is the interest paid to the lender; the remainder gets applied to the principal. Two identical amortizing loans, one 30/360 & the other actual/360, would actually have the same monthly payments, just different allocations of interest.

Example:

$1M Loan / 4% Interest Rate / 30-yr Ammoritization / March Payment (31 day month)

30/360: 

  • Payment - $4,774.15
    • Interest - $3,333.33 ((4.00%/360)*30) * $1,000,000) 
    • Principal - $1,440.82

Actual/360:

  • Payment - $4,774.14
    • Interest - $3,444.44 ((4.00%/360)*31* $1,000,000)
    • Principal - $1,329.71
 
Jmrunk

No, an amortizing loan does not always imply 30/360 interest accrual. 30/360 & actual/360 are just ways to determine what portion of the fixed payment is the interest paid to the lender; the remainder gets applied to the principal. Two identical amortizing loans, one 30/360 & the other actual/360, would actually have the same monthly payments, just different allocations of interest.

Example:

$1M Loan / 4% Interest Rate / 30-yr Ammoritization / March Payment (31 day month)

30/360: 

  • Payment - $4,774.15
    • Interest - $3,333.33 ((4.00%/360)*30) * $1,000,000) 
    • Principal - $1,440.82

Actual/360:

  • Payment - $4,774.14
    • Interest - $3,444.44 ((4.00%/360)*31* $1,000,000)
    • Principal - $1,329.71

In the Actual/360 scenario, doesn't that mean that the loan won't fully pay off over a 30 year time frame? 

 

Sit rerum consequuntur eius voluptatem est ducimus nihil. Libero quidem dicta quis quo deleniti et et modi. Aut quod modi omnis ipsum a quis dolorem dignissimos. Non id sint quis quo. Perspiciatis rem soluta ut aut. Rerum harum perspiciatis culpa aut. Provident autem ea vitae labore quae.

Dolorum explicabo tenetur laboriosam eum. Tempora et alias voluptatem placeat debitis debitis consequatur dolor. Numquam quisquam architecto sequi.

Consequatur quae nostrum repudiandae aut enim ut. Qui rerum similique nesciunt beatae assumenda eius. Animi dicta et laborum unde magni. Et veritatis voluptatem est velit. Id quia quos et et qui blanditiis non.

Career Advancement Opportunities

July 2026 Investment Banking

  • Evercore 01 99.4%
  • Moelis & Company 01 98.9%
  • JPMorgan 01 98.3%
  • Guggenheim Partners 01 97.7%
  • Morgan Stanley 07 97.1%

Overall Employee Satisfaction

July 2026 Investment Banking

  • Moelis & Company No 99.4%
  • Morgan Stanley 02 98.9%
  • Evercore 01 98.3%
  • BMO Capital Markets 12 97.7%
  • Banco Santander 01 97.1%

Professional Growth Opportunities

July 2026 Investment Banking

  • Evercore 01 99.4%
  • Moelis & Company 01 98.9%
  • Morgan Stanley 06 98.3%
  • Goldman Sachs 01 97.7%
  • JPMorgan 01 97.1%

Total Avg Compensation

July 2026 Investment Banking

  • Vice President (15) $434
  • Associates (46) $258
  • 3rd+ Year Analyst (8) $210
  • 2nd Year Analyst (22) $179
  • Intern/Summer Associate (13) $156
  • 1st Year Analyst (79) $150
  • Intern/Summer Analyst (73) $101
notes
16 IB Interviews Notes

“... there’s no excuse to not take advantage of the resources out there available to you. Best value for your $ are the...”

Leaderboard

1
redever's picture
redever
99.2
2
kanon's picture
kanon
99.0
3
Secyh62's picture
Secyh62
99.0
4
BankonBanking's picture
BankonBanking
99.0
5
dosk17's picture
dosk17
98.9
6
Betsy Massar's picture
Betsy Massar
98.9
7
CompBanker's picture
CompBanker
98.9
8
GameTheory's picture
GameTheory
98.9
9
DrApeman's picture
DrApeman
98.9
10
bolo up's picture
bolo up
98.8
success
From 10 rejections to 1 dream investment banking internship

“... I believe it was the single biggest reason why I ended up with an offer...”