GST (9%) Formula Explained, With Examples
Every gst (9%) result comes from one formula. Once you understand what goes into it, you can sanity-check any figure you are given, whether by an employer, a bank, a teacher or another website.
The formula
GST = price × 9%; price with GST = price × 1.09.
What each input means
- Price before GST (S$): the value you enter in the calculator.
Example
For example, with these inputs:
- Price before GST (S$): 100
the calculator returns:
- GST at 9%: S$9.00
- Price including GST: S$109.00
How the result changes
The table keeps the other inputs at their example values and changes price before gst (s$).
| Price before GST (S$) | GST at 9% | Price including GST |
|---|---|---|
| 100 | S$9.00 | S$109.00 |
| 50 | S$4.50 | S$54.50 |
| 75 | S$6.75 | S$81.75 |
| 125 | S$11.25 | S$136.25 |
| 150 | S$13.50 | S$163.50 |
Why it matters
Singapore's tax system is simple by global standards, but the progressive bands, reliefs and the 9% GST still trip people up. A quick calculation helps you set aside the right amount before IRAS sends your notice of assessment, or check that a bill has been worked out correctly.
Tax planning in Singapore is mostly about timing and reliefs rather than complex structures. Topping up CPF, contributing to SRS and claiming every relief you qualify for can lower your marginal rate band, and the savings are larger for higher earners.
You are generally a tax resident if you are a citizen or PR who normally lives here, or a foreigner who has stayed or worked in Singapore for at least 183 days in the calendar year. Non-residents do not get personal reliefs and are taxed differently, which is why residency status matters so much for expatriates.
Singapore taxes individuals on income earned in Singapore, with progressive rates for residents that start at 0% on the first S$20,000 of chargeable income and rise to 24% on income above S$1 million. Tax is assessed a year in arrears: income earned in 2025 is assessed in Year of Assessment 2026.
Related calculations
- SRS Tax Savings Calculator: Shows how much tax you save by contributing to the Supplementary Retirement Scheme.
- CPF Cash Top-Up Tax Relief Calculator: Estimates the tax saved from Retirement Sum Topping-Up: up to S$8,000 for yourself and S$8,000 for family members.
- Rental (Lease) Stamp Duty Calculator: Calculates stamp duty on a tenancy agreement of four years or less at 0.4% of the total rent.
- Singapore Income Tax Calculator: Calculates resident individual income tax from YA2024 onwards using Singapore's progressive rates from 0% to 24%.
Use the GST Calculator (9%) to plug in your own numbers.
Run your own numbers: GST Calculator (9%)