Our Methodology

Every calculator on Smart Calculator follows a rigorous process to ensure accuracy. Here's how we build and maintain our tools.

Rate Verification

Before hardcoding any Singapore government rate, we verify it against the current official source. This includes CPF contribution rates from cpf.gov.sg, tax brackets from iras.gov.sg, IPPT tables from MINDEF, and all other government figures.

Each rate file in our system includes a _verified block recording the verification date, method, and source URL.

Calculation Logic

Our calculators follow official rounding rules and calculation methods:

• CPF: Total = round to nearest dollar, Employee = always round down, Employer = Total minus Employee
• Tax: Progressive bracket calculation with cumulative flat amounts
• IPPT: Linear interpolation between verified scoring anchor points
• BMI: Singapore/Asia-Pacific thresholds (23.0 overweight, not 25.0)

Testing

We validate calculations against known test vectors — for example, a $5,000/month salary for a 30-year-old citizen should produce exactly $1,000 employee CPF, $850 employer CPF, and $4,000 take-home pay. These tests run automatically before every deployment.

Annual Updates

Singapore government rates typically change in January (CPF) and February (tax). We update all rate files within the first week of each change and re-verify against official sources.