Worked example: interest in Singapore
7 min read
Published September 23, 2025 • Updated February 2, 2026 • By DocketMath Team
Worked example: interest in Singapore
This walkthrough shows how a simple interest calculation can play out in a Singapore dispute, using the DocketMath interest calculator for the numbers: /tools/interest.
The goal is not to tell you what rate should apply in your matter, but to make the mechanics transparent:
- What inputs you need
- How they affect the result
- How to sanity‑check the output with small tweaks
All figures and assumptions below are illustrative only and not legal advice. Always confirm applicable rates and dates against Singapore law, rules of court, and your specific orders or contracts.
Example inputs
Imagine you are preparing a draft statement of claim in Singapore for an unpaid invoice.
Here is a simple illustration for Singapore. 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
- Principal sum claimed: SGD 250,000
- Invoice due date: 15 March 2021
- Claimed up to (calculation date): 30 June 2023
- Interest basis: Simple interest (no compounding)
- Interest periods:
- Pre‑writ contractual interest at 5.5% p.a.
- Post‑writ interest at 5.33% p.a. (illustrative, loosely tracking a typical court interest rate)
- Writ filed: 1 September 2022
You want:
- Pre‑writ interest on the unpaid sum from the day after due date until the day before the writ.
- Post‑writ interest from the writ date until your chosen calculation date.
Note:
In real matters, the applicable rate and start/end dates can depend on:
- Contract terms (e.g., “1.5% per month on overdue sums”)
- Statutory or court‑ordered interest rules
- Whether you are calculating pre‑judgment or post‑judgment interest
Always check the actual instrument and any orders. The example below is purely mechanical.
Mapping the scenario to calculator inputs
In DocketMath’s interest calculator for Singapore, you might set up two separate interest periods on the same principal:
**1. Pre‑writ period (contractual interest)
- Jurisdiction:
Singapore (SG) - Calculation mode:
Simple interest - Principal:
250,000 - Currency:
SGD - Start date:
16 March 2021
(the day after payment was due) - End date:
31 August 2022
(the day before the writ) - Annual rate:
5.5% - Compounding:
None - Day‑count convention:
Actual/365(illustrative; choose what aligns with your method or instructions)
**2. Post‑writ period (court‑style interest)
- Jurisdiction:
Singapore (SG) - Calculation mode:
Simple interest - Principal:
250,000 - Currency:
SGD - Start date:
1 September 2022 - End date:
30 June 2023 - Annual rate:
5.33% - Compounding:
None - Day‑count convention:
Actual/365
You can model this as either:
- Two separate runs in the calculator, or
- A multi‑period setup (if you prefer to see a combined breakdown in one run).
For this worked example, we’ll treat them as two segments and then add the totals.
Example run
Below is a step‑by‑step breakdown using simple interest:
[ \text{Interest} = \text{Principal} \times \text{Rate} \times \frac{\text{Days}}{\text{Day‑count base}} ]
We’ll use Actual/365, so the base is 365 days.
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.
1. Count the days in each period
Pre‑writ period: 16 Mar 2021 – 31 Aug 2022
Break it into calendar chunks for transparency:
- 16 Mar 2021 – 31 Dec 2021
- 1 Jan 2022 – 31 Aug 2022
Use actual day counts (DocketMath does this automatically, but it’s helpful to see the logic).
16 Mar 2021 – 31 Dec 2021
- March: 16–31 → 16 days
- April: 30
- May: 31
- June: 30
- July: 31
- August: 31
- September: 30
- October: 31
- November: 30
- December: 31
Total 2021 days:
[ 16 + 30 + 31 + 30 + 31 + 31 + 30 + 31 + 30 + 31 = 291 \text{ days} ]
1 Jan 2022 – 31 Aug 2022
- January: 31
- February: 28 (2022 is not a leap year)
- March: 31
- April: 30
- May: 31
- June: 30
- July: 31
- August: 31
Total 2022 days (to 31 Aug):
[ 31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 = 243 \text{ days} ]
Total pre‑writ days:
[ 291 + 243 = 534 \text{ days} ]
Post‑writ period: 1 Sep 2022 – 30 Jun 2023
Break into:
- 1 Sep 2022 – 31 Dec 2022
- 1 Jan 2023 – 30 Jun 2023
1 Sep 2022 – 31 Dec 2022
- September: 30
- October: 31
- November: 30
- December: 31
Total:
[ 30 + 31 + 30 + 31 = 122 \text{ days} ]
1 Jan 2023 – 30 Jun 2023
- January: 31
- February: 28 (2023 is not a leap year)
- March: 31
- April: 30
- May: 31
- June: 30 (up to 30 June inclusive)
Total:
[ 31 + 28 + 31 + 30 + 31 + 30 = 181 \text{ days} ]
Total post‑writ days:
[ 122 + 181 = 303 \text{ days} ]
Pitfall:
A common source of discrepancy is whether start and end dates are treated as inclusive or exclusive.
- Some methods count interest from (and including) the start date, up to (but excluding) the end date.
- Others treat both dates as inclusive in certain contexts.
DocketMath lets you see the exact day counts. Always align the setting with your instructions or the relevant rule.
2. Calculate pre‑writ interest
Inputs:
- Principal: SGD 250,000
- Annual rate: 5.5% (0.055)
- Days: 534
- Day‑count base: 365
[ \text{Pre‑writ interest} = 250{,}000 \times 0.055 \times \frac{534}{365} ]
First compute the year fraction:
[ \frac{534}{365} \approx 1.462 ]
Then:
[ 250{,}000 \times 0.055 = 13{,}750 ]
[ 13{,}750 \times 1.462 \approx 20{,}098. \text{ (rounded)} ]
So:
- Pre‑writ interest (16 Mar 2021 – 31 Aug 2022): ≈ SGD 20,098
If you plug the same inputs into DocketMath’s /tools/interest calculator with Actual/365, you should see a very close (or identical, depending on rounding) figure.
3. Calculate post‑writ interest
Inputs:
- Principal: SGD 250,000
- Annual rate: 5.33% (0.0533)
- Days: 303
- Day‑count base: 365
[ \text{Post‑writ interest} = 250{,}000 \times 0.0533 \times \frac{303}{365} ]
Year fraction:
[ \frac{303}{365} \approx 0.8301 ]
Then:
[ 250{,}000 \times 0.0533 = 13{,}325 ]
[ 13{,}325 \times 0.8301 \approx 11{,}060. \text{ (rounded)} ]
So:
- Post‑writ interest (1 Sep 2022 – 30 Jun 2023): ≈ SGD 11,060
4. Combine the totals
Add the two interest components:
[ \text{Total interest} \approx 20{,}098 + 11{,}060 = 31{,}158 ]
Overall picture:
| Component | Period | Rate | Days | Interest (SGD, approx.) |
|---|---|---|---|---|
| Pre‑writ | 16 Mar 2021 – 31 Aug 2022 | 5.5% | 534 | 20,098 |
| Post‑writ | 1 Sep 2022 – 30 Jun 2023 | 5.33% | 303 | 11,060 |
| Total | 16 Mar 2021 – 30 Jun 2023 | — | 837 | 31,158 |
If you were preparing a draft, you might summarise (numbers illustrative):
Interest on SGD 250,000 at 5.5% per annum from 16 March 2021 to 31 August 2022 and at 5.33% per annum from 1 September 2022 to 30 June 2023, calculated on a simple
Sensitivity check
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.
If an assumption is uncertain, document it alongside the calculation so the result can be re-run later.