How to Calculate GST (Add or Remove) With Examples
GST (Goods and Services Tax) is added to most products and services. Business owners, freelancers and shoppers all need to work out GST — either adding it to a base price or extracting it from a total that already includes it. Here's how both calculations work.
Adding GST to a base amount
When you have a price before tax and want the final price:
GST = Base × (Rate ÷ 100) | Total = Base + GST
Example: ₹1,000 at 18% → GST = ₹180, Total = ₹1,180.
Removing GST from an inclusive total
When a price already includes GST and you want the base amount:
Base = Total × 100 ÷ (100 + Rate) | GST = Total − Base
Example: ₹1,180 inclusive at 18% → Base = ₹1,000, GST = ₹180.
Common GST rates
- 5% — essentials and some food items
- 12% — processed foods, certain goods
- 18% — most goods and services
- 28% — luxury and premium items
Step-by-step: calculate GST
- Open the GST Calculator.
- Enter the amount and choose the GST rate (or a custom one).
- Select "Add GST" or "Remove GST".
- Click Calculate to see the base, GST and total.
Frequently Asked Questions
What's the difference between exclusive and inclusive prices?
An exclusive price is before GST; you add tax on top. An inclusive price already contains GST; you extract it to find the base.
What are CGST, SGST and IGST?
For sales within a state, GST splits into CGST and SGST. For sales between states, a single IGST applies. The total rate is the same.
Can I use a custom rate?
Yes. The calculator includes standard rates plus a custom option for any percentage.
Is this an official tax tool?
No — it's a helper for quick calculations. Always confirm final figures with your accountant or official portal.
Does it work for other countries' VAT?
Yes. The maths is identical for any percentage-based sales tax or VAT.
Try the GST Calculator