ACT/360

API value: act_360

Also known as: Actual/360, A/360, French method, Eurozinsmethode

ACT/360 counts the real number of calendar days in each interest period and divides by a 360-day year. It is the market convention for euro money-market rates such as EURIBOR and €STR, so variable-rate loans and floating-rate Schuldschein tranches usually use it.

Rules

Step 1: count the days. $d$ is the actual number of calendar days from the start date (inclusive) to the end date (exclusive). No dates are adjusted: February has 28 or 29 days, March has 31.

Step 2: calculate the interest.

Formula:

$$I = B \cdot r \cdot \frac{d}{360}$$

With the terms:

$$\text{Interest} = \text{Balance} \cdot \text{Rate} \cdot \frac{\text{Actual days}}{360}$$

With the example numbers: 100,000 EUR at 4.00 % from 31 January to 28 February 2026, which is 28 calendar days.

$$I = 100{,}000 \cdot 0.04 \cdot \frac{28}{360} = 311.11$$

What this means in practice

• Longer months accrue more interest than shorter ones.
• Because a year has 365 or 366 days but is divided by 360, a full year accrues more than the nominal rate: 4.00 % nominal becomes about 4.056 % over 365 days and about 4.067 % in a leap year.
• The effective cost is therefore higher than the same nominal rate on a 30/360 basis. Keep this in mind when comparing offers.

Example

100,000 EUR at 4.00 % p.a., balance unchanged.

How to recognise it in a contract

• "Actual/360", "act/360", "taggenau/360" or "Eurozinsmethode".
• A variable rate defined as "EURIBOR + margin" or "€STR + margin". The reference rate itself is quoted on ACT/360, and most agreements apply the same basis to the all-in rate.

Related

• Guides overview
• ACT/365
• German 30/360