What is the GST Calculator?
A GST calculator helps you add Goods and Services Tax on top of a base price, or reverse-calculate the base from a GST-inclusive total. It's the day-to-day tool every Indian shopkeeper, freelancer and finance team uses.
Supports all four standard slabs (5%, 12%, 18%, 28%) plus any custom rate.
Formula
GST amount = Base × Rate / 100 (add) · Base = Total × 100 / (100 + Rate) (reverse)
- Base — Pre-tax price
- Rate — Applicable GST percentage
Step-by-step example
Setup: Invoice base ₹10,000 at 18% GST.
- GST = 10,000 × 18 / 100 = ₹1,800
- Total = ₹11,800
- Reverse: 11,800 × 100 / 118 = ₹10,000
Answer: GST = ₹1,800 · Total = ₹11,800
Frequently asked questions
Which slab applies to my product?
Check the official GST rate finder or your CA. Most services attract 18%; daily essentials often 5% or nil.
Is the slab the same across India?
Yes. GST is a unified national tax. CGST + SGST (intra-state) or IGST (inter-state) add up to the same total rate.