GST Calculator
Add GST to a net amount or remove it from a GST-inclusive total — with the net price, GST amount and gross broken out.
How it works
Add GST: GST = amount × rate, gross = amount + GST · Remove GST: net = amount ÷ (1 + rate), GST = amount − net
GST (Goods and Services Tax) is a percentage added on top of the net price. To add it, multiply the net amount by the rate. To back it out of a GST-inclusive total, divide by (1 + rate) rather than subtracting the percentage — the tax was charged on the smaller net amount, so subtracting the rate from the gross figure over-removes it. Choose a common slab (5/12/18/28%) or enter a custom rate.
Worked example
Adding 18% GST to a $1,000 net amount gives $180 GST and a $1,180 gross total. To remove 18% GST from a $1,180 inclusive total, divide: 1,180 ÷ 1.18 = $1,000 net, so the GST is $180 — not the $212.40 you would wrongly get by taking 18% of $1,180.
Frequently asked questions
How do I remove GST from an inclusive price?
Divide the gross amount by (1 + rate), not by subtracting the percentage. A $1,180 total at 18% GST is 1,180 ÷ 1.18 = $1,000 net, so the GST is $180. Subtracting 18% of $1,180 would wrongly give $967.60.
What are the common GST rates?
Many GST systems use tiered slabs — for example 5%, 12%, 18% and 28% in India — applied to different categories of goods and services. Countries like Australia, Singapore and Canada use a single flat GST rate instead. Pick the slab that applies to your item or enter a custom rate.
Is GST the same as VAT?
Arithmetically, yes — both are multi-stage consumption taxes calculated the same way: multiply to add, divide by (1 + rate) to remove. The names and administrative rules differ by country, but the math in this calculator is identical.
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Educational estimate, not financial advice.