Worked example: Interest in Brazil

Example inputs

Run this scenario in DocketMath using the Interest calculator.

This worked example shows how to use DocketMath’s interest calculator for a Brazil (BR) scenario. The goal is to demonstrate a complete, jurisdiction-aware input set and to highlight how changing certain fields affects the output.

Scenario (example)

You have an amount that accrued interest over time. You want to compute simple interest for 180 days using a simplified, tool-driven approach for Brazil.

Primary CTA / tool link: /tools/interest

Inputs you’ll enter in DocketMath (Interest → BR)

Check the following boxes as you prep your data:

• Principal (the starting amount)
• Annual interest rate (nominal, as required by the tool’s Brazil rules)
• Start date and end date (to determine day count)
• Interest type (simple vs. compounded—if the tool asks)
• Day-count convention (if exposed by the tool)
• Any “already accrued” base date (if your workflow requires it)

Concrete values for this example

Assume:

• Principal: BRL 10,000.00
• Annual interest rate: 12%
• Calculation period: from 2025-01-15 to 2025-07-14
• Compounding: none (simple interest setting in the tool)
• Day count: tool-driven actual days between the two dates (use the “Days counted” value DocketMath shows)

Before running, sanity-check the dates:

• Start: 15 Jan 2025
• End: 14 Jul 2025
• Total days: 180 days (inclusive/exclusive handling is tool-specific—use what DocketMath displays as the computed day count).

Quick math reference (so you can spot tool errors)

If the tool applies simple interest with a 365-day year:

• Daily factor = 0.12 / 365
• Interest = 10,000 × (0.12/365) × 180
• Interest ≈ 10,000 × 0.059178…
• Interest ≈ BRL 591.78

The tool may round at intermediate steps; treat the rounded-cents output as the “source of truth” for the worked example.

Example run

Open DocketMath and select the interest calculator for Brazil (BR):

• Tool: /tools/interest

Run the Interest calculator using the example inputs above. Review the breakdown for intermediate steps (segments, adjustments, or rate changes) so you can see how each input moves the output. Save the result for reference and compare it to your actual scenario.

Step-by-step inputs (as entered)

1. Select jurisdiction: **Brazil (BR)
2. Set:

   • Principal: 10,000.00
   • Annual rate: 12.00%
   • Start date: 2025-01-15
   • End date: 2025-07-14
   • Interest type: simple
   • Leave other advanced toggles at defaults unless the tool presents Brazil-specific options you must choose (e.g., a particular day-count convention).

What DocketMath calculates (example output)

After you click Calculate, DocketMath returns:

• Days counted: 180 days
• Computed interest: BRL 591.78
• Amount with interest (principal + interest): BRL 10,591.78

You can treat those figures as the baseline for the rest of this example.

Interpreting the result

Use the output in three practical ways:

1. Budgeting / settlement ranges

   • Baseline total due over 180 days: BRL 10,591.78
2. Audit trail

   • Record the main drivers you entered and the tool reported:

     • principal (10,000.00)
     • annual rate (12%)
     • day count (180)
3. Sensitivity testing

   • Change one parameter at a time (rate, period length, or interest type) to see how the total moves.

Sensitivity check

A worked example is most useful if you can predict how changes alter the result. Below are targeted “what if” variations that stress the main drivers in the Brazil interest calculation.

To test sensitivity, change one high-impact input (like the rate, start date, or cap) and rerun the calculation. Compare the outputs side by side so you can see how small input shifts affect the result.

A. Change the annual interest rate (12% → 10%)

Keep everything else the same:

• Principal: 10,000.00
• Period: 2025-01-15 to 2025-07-14 (180 days)
• Simple interest

Expected directional effect: interest decreases.

If the tool uses simple interest:

• Interest ≈ 10,000 × (0.10/365) × 180
• Interest ≈ 10,000 × 0.049315…
• Interest ≈ BRL 493.15

What you should look for in DocketMath:

• Computed interest should be near BRL 493.15 (allow for rounding)
• Total due should be near BRL 10,493.15

B. Extend the period by 60 more days (180 → 240 days)

Now assume the tool counts 240 days (illustration—ensure your new end date produces 240 in DocketMath).

• Principal: 10,000.00
• Rate: 12%
• Simple interest
• Days: 240

Directional effect: interest increases proportionally for simple interest.

Expected:

• Interest ≈ 10,000 × (0.12/365) × 240
• Interest ≈ 10,000 × 0.078904…
• Interest ≈ BRL 789.04

Tool verification targets:

• Interest near BRL 789.04
• Total due near BRL 10,789.04

C. Switch from simple to compounded (if the tool supports it)

Compounding can materially change totals over time.

Directional effect:

• With a compounding frequency (e.g., monthly/quarterly/daily), the amount usually increases vs. simple interest for the same nominal annual rate and period.

D. Validate day-count conventions

Day-count handling often explains “small but real” differences (e.g., 179 vs. 180 days, leap-year behavior, whether endpoints are inclusive).

Practical approach:

• Re-run the same scenario and confirm the “Days counted” line in DocketMath.
• Then change only the end date by 1 day and observe whether the days counter changes by 1.

Checklist:

Sensitivity results table (baseline vs. variations)

Use this table as a quick “reasonableness check” against the tool outputs you generate in your own run.

Related reading

• Interest rule lens: Maine — The rule in plain language and why it matters
• Common interest mistakes in Rhode Island — Common errors and how to avoid them
• Worked example: interest in Maine — Worked example with real statute citations