How to Calculate GST in 2026

GST is India's unified tax system. Whether you run a shop, freelance, or manage invoices, calculating GST correctly is essential.

GST Rate Slabs

India has 5 GST rates:

Rate	Applies To
0%	Essential food items
5%	Basic goods
12%	Standard goods
18%	Most services
28%	Luxury items

Step-by-Step: How to Calculate GST

For Adding GST (Exclusive)

Formula: GST = Base × Rate ÷ 100

Example: ₹1,000 at 18%

• GST = 1,000 × 18 ÷ 100 = ₹180
• Total = ₹1,180

For Removing GST (Inclusive)

Formula: Base = Total ÷ (1 + Rate ÷ 100)

Example: ₹1,180 at 18%

• Base = 1,180 ÷ 1.18 = ₹1,000
• GST = ₹180

CGST and SGST Split

For sales within the same state, GST is split:

• CGST (Central GST): 9%
• SGST (State GST): 9%

For inter-state sales, use IGST at 18%.

Common Mistakes

1. Using wrong HSN/SAC code
2. Forgetting CGST+SGST split
3. Not rounding to nearest rupee

Try Our Free GST Calculator

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Written by the ShopBill Pro Team.