Worked example: interest in Delaware

Run this scenario in DocketMath using the Interest calculator.

Calculating interest on a judgment in Delaware looks simple on paper, but the details matter:

• Which rate applies?
• From what date?
• Simple or compound?
• What happens if the rate changes mid-stream?

This worked example walks through a realistic Delaware scenario using the DocketMath interest calculator (see /tools) so you can see how the pieces fit together—without turning it into a math project.

Example inputs

We’ll build a concrete example, then show how each input affects the output in DocketMath.

Here is a simple illustration for Delaware. These values are for demonstration only and should be replaced with your actual inputs.

• Principal or amount: $120,000
• Rate or cap: 12%
• Start date: 2025-01-15
• End/as-of date: 2025-09-30

Scenario overview

Suppose:

• A Delaware Superior Court enters a money judgment.
• The judgment is for $250,000.
• The judgment is entered on March 15, 2021.
• You want to know the accrued interest as of October 1, 2024.
• Delaware law for this type of judgment leads you to use a fixed annual simple interest rate of 8%.

We’ll use these assumptions to set up the calculator.

Mapping the scenario to calculator fields

In the DocketMath interest calculator (/tools/interest), you’d configure something like:

1. Jurisdiction

   • Jurisdiction: Delaware (US-DE)
   • Reason: Ensures the tool uses Delaware-specific defaults or templates if available.

2. Principal and dates

   • Principal amount: 250,000.00
   • Start date (when interest begins): 2021-03-15
   • End date (calculation through): 2024-10-01
   • Day-count convention: Actual/365 (common for statutory simple interest; confirm for your use case)

3. Interest rate

   • Rate type: Fixed rate
   • Annual interest rate: 8%
   • Compounding: None (simple interest)
   • Application: Single continuous period (no stepped or changing rates in this base example)

4. Output preferences

   • Show:

     • Total interest
     • Total amount (principal + interest)
     • Daily rate
     • Period breakdown (by year)

Example run

With those inputs, DocketMath will:

1. Count the number of days between March 15, 2021 and October 1, 2024.
2. Apply the 8% annual simple interest rate.
3. Use the chosen day-count convention to convert days into a year fraction.
4. Multiply:

   • Principal × rate × time (in years).

You can sanity-check the math as follows.

1. Count the interest days

We’ll treat interest as accruing from March 15, 2021 up to but not including October 1, 2024, which is a common convention. (Always check how your court or statute defines the accrual period.)

Breakdown by period:

• March 15, 2021 → March 15, 2022: 365 days (no leap day in this span)
• March 15, 2022 → March 15, 2023: 365 days
• March 15, 2023 → March 15, 2024: 366 days (this span crosses Feb 29, 2024)
• March 15, 2024 → October 1, 2024:

  • March 15–31: 17 days
  • April: 30 days
  • May: 31 days
  • June: 30 days
  • July: 31 days
  • August: 31 days
  • September: 30 days
  • Total: 200 days

Total days of interest:

• 365 + 365 + 366 + 200 = 1,296 days

DocketMath performs this date math automatically, but it’s useful to understand that it is literally counting the days where interest accrues.

2. Convert days to years (Actual/365)

Using the Actual/365 convention:

• Time in years = 1,296 ÷ 365
• 1,296 ÷ 365 ≈ 3.5521 years

This is the “t” in the simple interest formula.

3. Apply the simple interest formula

Simple interest formula:

Interest = Principal × Rate × Time

Where:

• Principal = 250,000
• Rate = 8% = 0.08
• Time ≈ 3.5521 years

Compute:

1. Principal × Rate =
   250,000 × 0.08 = 20,000 per year

2. Multiply by time:
   20,000 × 3.5521 ≈ 71,042

So:

• Estimated interest ≈ $71,042
• Total (principal + interest) ≈ $321,042

In DocketMath you would see a breakdown similar to:

Daily interest is just:

• 71,042 ÷ 1,296 ≈ $54.82 per day

That per-day number is often what litigators and case managers want on hand for quick “as of” updates or for drafting settlement calculations.

4. How this looks in DocketMath

Using /tools/interest with the inputs above, you’d see:

• A summary card with:

  • Total interest
  • Total amount
  • Days counted
• A timeline or table showing:

  • Year-by-year interest
  • Daily rate and assumptions
• An Explain++ breakdown (if enabled) that shows each step in the calculation so you can validate the math for a Delaware filing or settlement memo.

Example year-by-year breakdown (rounded):

Minor rounding differences occur depending on whether you:

• Compute once with the full 1,296 days, or
• Compute period-by-period and then sum.

DocketMath’s Explain++ view makes those choices explicit so you can match your court’s preferred style.

Sensitivity check

The real value of a calculator is not just one number—it’s seeing how sensitive that number is to different assumptions.

Below are a couple of quick “what if” tweaks to our Delaware example to illustrate how the output changes.

1. What if the rate is 5% instead of 8%?

Keep everything else the same:

• Principal: $250,000
• Start date: 2021-03-15
• End date: 2024-10-01
• Days: 1,296
• Rate: 5% (0.05)
• Time: 1,296 ÷ 365 ≈ 3.5521 years

Interest:

• 250,000 × 0.05 = 12,500 per year
• 12,500 × 3.5521 ≈ $44,401

Compare:

A 3‑percentage‑point difference in the rate produces roughly a $26,600 difference in interest over this period.

2. What if interest starts later?

Assume the same 8% rate, but interest starts on June 1, 2021 instead of March 15, 2021.

New period: June 1, 2021 → October 1, 2024.

Days:

• June 1, 2021 → June 1, 2022: 365
• June 1, 2022 → June 1, 2023: 365
• June 1, 2023 → June 1

Related reading

• Worked example: deadlines in New York

• Interest rule lens: Maine

• How to calculate deadlines in Delaware

• Why we started the DocketMath blog