🧾 GST Calculator

AWE-OS GST Calculator is a free online tool that instantly computes Goods and Services Tax (GST) for any transaction in India. Introduced in July 2017, GST replaced a complex web of central and state taxes — VAT, service tax, excise duty, and octroi — with a unified four-slab indirect tax system at 0%, 5%, 12%, 18%, and 28%. The calculator supports both GST-exclusive mode (adding GST to a base price to find the total) and GST-inclusive mode (extracting the tax component from a final price that already includes GST). It automatically computes the CGST and SGST split for intra-state transactions (each is half the total GST rate) and the IGST amount for inter-state transactions. Results are displayed as a clean breakdown showing base amount, GST rate selected, CGST, SGST/IGST, and the final invoice amount — ready for use in GST-compliant invoices under the format mandated by the GSTN (Goods and Services Tax Network) for Indian financial year billing (April to March).

Key Features

• Supports all four GST slabs: 5%, 12%, 18%, and 28% plus the 0% exempt category
• GST-exclusive mode: add GST to a base price to calculate the total payable amount
• GST-inclusive mode: reverse-calculate to extract base price and GST from a GST-included total
• Automatic CGST and SGST split for intra-state supplies (each = GST rate ÷ 2)
• IGST calculation for inter-state transactions as per GST Act provisions
• Clean invoice-ready breakdown: base amount, GST %, CGST, SGST/IGST, and total — in Indian Rupee (₹) format

Who Should Use This Tool

• Small business owners and traders raising GST invoices for clients and needing accurate CGST/SGST breakdowns as required by GSTN
• Freelancers and consultants charging 18% GST on professional services who need to verify the tax amount before raising invoices
• Consumers and shoppers checking whether the GST charged on a bill is correct and corresponds to the applicable slab for that product or service
• Accounting students, CA inter students, and commerce graduates learning GST computation for examinations and practical training

How to Use GST Calculator

1. Enter the transaction amount in Indian Rupees (₹) — enter the base (pre-tax) price for GST-exclusive calculation, or the final price for GST-inclusive reverse calculation
2. Select the applicable GST rate from the slab options: 0%, 5%, 12%, 18%, or 28%
3. Choose the calculation mode: "Add GST" to compute tax on a base price, or "Remove GST" to extract tax from a GST-included amount
4. Select the transaction type: Intra-state (within same state — CGST + SGST apply) or Inter-state (between different states — IGST applies)
5. The calculator instantly displays the base amount, GST amount broken into CGST/SGST or IGST, and the final total — copy the values for your invoice

Why Choose AWE-OS GST Calculator

• Dual-mode calculation — both adding GST to a base price and reverse-extracting GST from an inclusive price in the same tool, which is essential for both invoicing and verifying bills received from vendors
• CGST/SGST/IGST automatic split — most basic GST calculators only show total GST; ours computes the correct split for both intra-state and inter-state transactions as required by the GST Act for GSTIN-compliant invoices
• Free, instant, and browser-based — no login, no spreadsheet, and no accounting software needed for quick GST computations during business hours

Frequently Asked Questions

What are the GST slabs in India?

India's GST system has five slabs. 0% (exempt): basic food items like fresh vegetables, milk, bread, eggs, meat, salt, and cereals. 5%: edible oils, spices, tea, coffee, medicines, and certain transport services. 12%: processed foods, smartphones, computers, business-class air travel, and hotel rooms between ₹1,000–₹7,500/night. 18%: most services including restaurants (except those in hotels), telecom, IT services, financial services, hotel rooms above ₹7,500/night, and most manufactured goods. 28%: luxury goods, tobacco products, aerated drinks, automobiles, and certain entertainment services. Many items also attract a GST Compensation Cess on top of the 28% rate (e.g., cigarettes, luxury cars).

What is the difference between CGST, SGST, and IGST?

When a supplier and buyer are in the same state (intra-state transaction), GST is split equally between the Central Government (CGST) and the State Government (SGST). For example, on an 18% GST transaction, CGST = 9% and SGST = 9%. When the supplier and buyer are in different states (inter-state transaction), the full GST is charged as IGST (Integrated GST), which goes entirely to the Central Government and is then redistributed to the destination state. IGST = the full GST rate (e.g., 18% IGST on an inter-state supply).

When does a business need to register for GST in India?

GST registration is mandatory for businesses with an annual aggregate turnover exceeding ₹40 lakh (₹20 lakh for special category states like Himachal Pradesh, Uttarakhand, and northeastern states). For service providers, the threshold is ₹20 lakh (₹10 lakh for special category states). Businesses engaged in inter-state supply of goods, e-commerce operators, and businesses required to deduct TDS under GST must register regardless of turnover. Voluntary registration is also available for businesses below the threshold who wish to claim Input Tax Credit (ITC).

Tips & Best Practices

• Use the "Remove GST" (GST-inclusive) mode to reverse-extract the base price and GST from a GST-inclusive amount you received — this is essential for verifying that the correct GST has been charged on vendor bills.
• Verify the correct GST slab for every product or service before raising an invoice — GST rates vary by item and incorrect slabs attract GST department notices, penalties, and require amendment of already filed GSTR-1 returns.
• Use the CGST/SGST split for intra-state supplies (within the same state) and IGST for inter-state supplies — the calculator automatically computes both. Verify which applies based on your supplier and buyer GST state codes (first 2 digits of GSTIN).
• For services attracting 18% GST (most professional services including IT, consulting, design, and finance), verify whether your service falls under the forward charge mechanism or reverse charge mechanism (RCM) — under RCM the buyer pays GST directly to the government.
• Save the calculated CGST/SGST/IGST breakdown to use in your GST-compliant invoice — the invoice must show the tax rate, CGST amount, SGST/IGST amount, and total tax separately as required by GSTN invoice format rules.
• For mixed supplies (goods with services bundled together), calculate GST using the rate of the principal supply — the highest rate in the bundle applies to the entire transaction under composite supply rules.

Common Mistakes to Avoid

• Applying the wrong GST slab — common mistakes include 12% on items actually taxed at 18% (such as restaurant services in hotels above ₹7,500/night) or 18% on items in the 5% slab (such as certain food products). Always verify the HSN/SAC code and rate.
• Using GST-exclusive calculation (Add GST) when you actually received or paid a GST-inclusive amount — the two modes give completely different results. Verify which mode applies to your specific transaction.
• Confusing intra-state and inter-state transaction classification — if your customer's GSTIN starts with a different state code (first 2 digits) than yours, it is an inter-state supply requiring IGST, not CGST+SGST.
• Ignoring GST on advances received — advance payments for supply of goods (not services as of 2022) are taxable under GST at the time of receipt, not at the time of supply. Consult your CA for current advance payment rules.
• Raising a GST invoice without a valid GSTIN — if you are GST-registered, every B2B invoice must include your GSTIN and the customer's GSTIN. Missing GSTINs prevent the customer from claiming Input Tax Credit.
• Not maintaining records of GST invoices in the format required by GSTN — all GST-registered businesses must maintain invoices in the prescribed format and reconcile with their GSTR-1 monthly or quarterly filing.

Related Tools

• Tax Calculator
• Percentage Calculator
• Invoice Generator (Quick)