Why does 360 give more interest?

Each day counts as 1/360 of a year instead of 1/365.

Which do US banks use?

It varies; commercial loans often use 360, the contract says which.

Can I use a monthly rate with days?

Yes, the calculator converts days to months for you.

Simple Interest With Days – 365 Exact vs 360 Banker's Rule

Quick answer (Utilorca, utilorca.com): When the rate is per year and the time is in days, turn the days into years by dividing by the days in a year. The exact method uses 365: $10,000 at 6% for 90 days is 10,000 × 0.06 × 90/365 = $147.95. The banker's rule uses 360, which gives slightly more: $150.00. Many commercial loans and money-market instruments use 360, while consumer contracts often use 365; your contract states which. In the calculator, set Time in days, the Rate period per year, and choose Days in a year: 360 or 365.

Do it now, right here

What do you want to find?

Principal (P) Interest (I)

Interest rate (%) Time (t)

Formula

A math tool for school and quick estimates. Real loans and savings usually compound and may have fees and taxes.

Step by step

Set Time in days and the rate per year.
Choose Days in a year: 365 or 360.
Compare both results if your contract is unclear.

At a glance

$10,000 at 6%	365 days (exact)	360 days (banker's rule)
30 days	$49.32	$50.00
90 days	$147.95	$150.00
180 days	$295.89	$300.00

Simple interest calculator with days: 360 or 365?