Key takeaways
What this article covers, in order:
- Working out GST yourself
- Step by step
- How HelloBooks helps
- Frequently asked questions
Calculating GST by hand is simple once you know the formula — and free tools do it instantly.
Working out GST yourself
To add GST, multiply the taxable value by the rate; to find the GST inside a GST-inclusive price, divide by (100 + rate) and multiply by the rate. A free GST calculator does both in one tap.
- GST amount = taxable value × rate ÷ 100.
- GST-inclusive price = taxable value × (1 + rate ÷ 100).
- Reverse calculation: GST = inclusive price × rate ÷ (100 + rate).
Step by step
- Open the official GST portal or a free GST tool.
- Enter your details for the period or transaction.
- Review the result and keep a copy for your records.
Rates change at GST Council meetings, so always confirm the current figure for your exact HSN or SAC code on the CBIC rate finder or the GST portal before you print it on an invoice.
How HelloBooks helps
HelloBooks turns the compliance steps above into a few clicks. HelloBooks is free GST accounting software for Indian businesses: you can raise GST-compliant invoices with the correct HSN or SAC code, track input tax credit against your GSTR-2B, and file unlimited GSTR-1 and GSTR-3B returns from one dashboard.
- GST-ready invoicing with automatic CGST / SGST / IGST split and HSN or SAC codes.
- GSTR-2B reconciliation so you only claim the input tax credit you are actually entitled to.
- GSTR-1 and GSTR-3B filing free, with GSTR-9 generated ready to file and e-invoicing on higher plans.
- Due-date reminders so a late fee never catches you by surprise.
Thousands of founders, freelancers and accountants in India run their books on HelloBooks — you can start free, with no credit card.
Frequently asked questions
Is a GST calculator free to use?
Yes — most online GST calculators, including the one in HelloBooks, are free. Every invoice you raise in HelloBooks is calculated automatically.
Do I need a CA for this?
No — the process is online and self-service. A professional is optional and only needed for complex or disputed cases.
Does HelloBooks offer this for free?
Yes. HelloBooks is free GST accounting software for India: free GSTR-1 and GSTR-3B filing, GST-ready invoicing and GSTR-2B reconciliation, no credit card to start.
