How to Calculate GST: Add or Remove GST from Any Amount Easily
Introduction
GST (Goods and Services Tax) is a crucial part of every business transaction in India.
Whether you’re a clinic owner, a small lab, or a medical supplier, knowing how to calculate GST is essential for accurate billing and tax compliance.
This article will help you clearly understand two things:
How to add GST to the base price of a product or service
How to remove GST from the total price that already includes GST
Let’s break it down step by step using very simple examples.
1. How to Add GST to a Basic Amount
This is needed when you have a base price and want to add GST to find the final price (selling price or invoice amount).
Formula to Add GST:
Final Amount = Base Amount + (Base Amount × GST%)
Example:
Suppose you’re selling dental gloves with a base price of ₹1,000 and GST is 12%.
GST Amount = ₹1,000 × 12% = ₹120
Final Invoice Amount = ₹1,000 + ₹120 = ₹1,120
Tip:
Use this method while raising bills or creating GST invoices.
2. How to Remove GST from a Total Amount
This is needed when you have a total amount (which already includes GST), and you want to find the base price and GST amount separately.
Formula to Remove GST:
Base Price = Total Amount × (100 / (100 + GST%))
GST Amount = Total Amount – Base Price
Example:
Let’s say you received ₹1,120 from a customer, and this includes 12% GST.
Base Price = ₹1,120 × (100 / 112) = ₹1,000
GST Amount = ₹1,120 – ₹1,000 = ₹120
Tip:
Use this method while doing reverse calculations or preparing GST returns.
3. Quick Reference Table
GST Rate | Multiply by (for base value) |
|---|---|
5% | 100 / 105 |
12% | 100 / 112 |
18% | 100 / 118 |
28% | 100 / 128 |
Use these factors when removing GST from a total.
4. Bonus: GST Calculation Shortcut in Excel
You can use these formulas in Excel for faster work:
To add GST: =BaseAmount*(1+GST%)
To remove GST: =TotalAmount*(100/(100+GST%))
This makes billing and reconciliation faster, especially for small clinics and distributors.
Conclusion
Whether you’re adding GST to quote a customer or removing GST for tax filing, understanding how to calculate GST correctly is crucial.
It helps avoid errors, builds customer trust, and ensures compliance.
Now that you’ve learned both methods:
Use the Addition Formula when raising invoices
Use the Removal Formula when back-calculating or filing returns
Stay consistent and accurate to avoid mismatches during GST audits.
If you’re a Healthcare MSME looking to automate this, explore billing tools like TallyPrime, Zoho Books, or even Excel-based GST calculators.