GST Reverse Calculation: Find Original Price from GST-Inclusive Amount

!Tax calculation and invoicing

You see a price tag of ₹1,180 with "GST included." But what was the original price before GST? And how much GST is actually included?

This is reverse GST calculation—essential for businesses filing returns, consumers understanding pricing, and accountants reconciling invoices. In this guide, we'll cover the formulas for every GST rate. Use our VAT Calculator for instant calculations.

The Reverse GST Formula

`` Original Price = GST-Inclusive Price / (1 + GST Rate/100) `

Or equivalently: ` Original Price = GST-Inclusive Price × 100 / (100 + GST Rate) `

And to find the GST amount: ` GST Amount = GST-Inclusive Price - Original Price `

Formulas by GST Rate

5% GST Reverse Calculation

` Original Price = GST-Inclusive Price / 1.05 GST Amount = GST-Inclusive Price × 5/105 ` Example: Total bill ₹1,050

• Original Price = 1,050 / 1.05 = ₹1,000
• GST (5%) = ₹50

12% GST Reverse Calculation

` Original Price = GST-Inclusive Price / 1.12 GST Amount = GST-Inclusive Price × 12/112 ` Example: Total bill ₹5,600

• Original Price = 5,600 / 1.12 = ₹5,000
• GST (12%) = ₹600

18% GST Reverse Calculation

` Original Price = GST-Inclusive Price / 1.18 GST Amount = GST-Inclusive Price × 18/118 ` Example: Total bill ₹11,800

• Original Price = 11,800 / 1.18 = ₹10,000
• GST (18%) = ₹1,800

28% GST Reverse Calculation

` Original Price = GST-Inclusive Price / 1.28 GST Amount = GST-Inclusive Price × 28/128 ` Example: Total bill ₹12,800

• Original Price = 12,800 / 1.28 = ₹10,000
• GST (28%) = ₹2,800

Quick Reference Table

GST Rate	Divide By	To Get Original
5%	1.05	Price × 100/105
12%	1.12	Price × 100/112
18%	1.18	Price × 100/118
28%	1.28	Price × 100/128

Worked Examples

Example 1: Restaurant Bill

Total paid: ₹1,416 (includes 18% GST)

Calculation:

• Original amount = 1,416 / 1.18 = ₹1,200
• GST = 1,416 - 1,200 = ₹216

Breakdown:

• Food value: ₹1,200
• GST (18%): ₹216
• Total: ₹1,416

Example 2: Electronics Purchase

Total paid: ₹51,200 (includes 28% GST)

Calculation:

• Original amount = 51,200 / 1.28 = ₹40,000
• GST = 51,200 - 40,000 = ₹11,200

Breakdown:

• Product value: ₹40,000
• GST (28%): ₹11,200
• Total: ₹51,200

Example 3: Service Provider

Invoice total: ₹23,600 (includes 18% GST)

Calculation:

• Original amount = 23,600 / 1.18 = ₹20,000
• GST = 23,600 - 20,000 = ₹3,600

Split into CGST and SGST:

• CGST (9%): ₹1,800
• SGST (9%): ₹1,800
• Total GST: ₹3,600

GST Components (CGST, SGST, IGST)

GST is divided depending on transaction type:

Intra-State (Within Same State)

Total GST	CGST	SGST
5%	2.5%	2.5%
12%	6%	6%
18%	9%	9%
28%	14%	14%

Inter-State (Different States)

Total GST	IGST
5%	5%
12%	12%
18%	18%
28%	28%

Excel Formulas

Reverse Calculate Original Price

`excel =A1/(1+B1/100) ` Where A1 = Inclusive amount, B1 = GST rate percentage

Calculate GST Amount

`excel =A1-A1/(1+B1/100) `

Or: `excel =A1*B1/(100+B1) ``

Common GST Rates by Category

Category	GST Rate
Essential goods	0% (Exempt)
Food grains, eggs	0%
Packaged food items	5%
Processed foods	12%
Restaurants (non-AC)	5%
Restaurants (AC)	5%*
Hotels (₹1,000-7,500/night)	12%
Hotels (>₹7,500/night)	18%
Most services	18%
Software, IT services	18%
Automobiles	28%
Luxury goods	28% + Cess

*Note: GST rates may change; verify current rates.

Common Mistakes

Mistake 1: Wrong Formula Direction

Wrong: Original ÷ (1 + rate) → gives LOWER value Right: Inclusive ÷ (1 + rate) → gives original

Mistake 2: Using Percentage Directly

Wrong: ₹1,180 ÷ 18 = ₹65.55 (incorrect!) Right: ₹1,180 ÷ 1.18 = ₹1,000

Mistake 3: Confusing Forward and Reverse

Forward: Original × (1 + rate) = Inclusive Reverse: Inclusive ÷ (1 + rate) = Original

Business Applications

For Input Tax Credit (ITC)

When claiming ITC, you need GST amounts from invoices:

• Verify GST amounts on supplier invoices
• Reverse calculate if only total is given
• Match with GSTR-2B for reconciliation

For Expense Reporting

When submitting expense reports:

• Original amount is the expense
• GST is separately claimable (if applicable)
• Some companies require split reporting

For Pricing Decisions

When setting MRP with inclusive GST:

• Decide target selling price (inclusive)
• Reverse calculate base price
• Verify margins are acceptable

Frequently Asked Questions

How do I know the GST rate from an inclusive price?

You need the product/service category to determine applicable GST rate. The invoice should mention the rate applied.

What if product has multiple GST components?

Composite supplies are taxed at the rate of the principal supply. Mixed supplies take the highest applicable rate.

Is GST calculated on MRP or actual selling price?

GST is calculated on:

• Transaction value (actual selling price)
• Not necessarily MRP

How to handle discounts?

GST is calculated on the discounted price if discount is mentioned on invoice and given at time of sale.

---

Related Articles

• Income Tax Old vs New Regime
• CTC to Take Home Salary Calculation
• How to Calculate Percentage Increase
• Discount Calculator Guide
• HRA Exemption Calculation