You’re at the market. The shopkeeper says 800g of chocolate costs ₹350. You only have ₹134. How much chocolate do you get? Or you want exactly 75g of sugar — how much should you pay?
Most people guess, or trust the shopkeeper blindly. But there’s a simple mathematical rule — called the Rule of Three or proportional calculation — that gives you the exact answer in seconds. And our free Rate Calculator does all this math instantly for you, on any device.
The Two Questions You Can Answer
Every price-quantity problem at a market falls into one of two types:
| Question Type | What You Know | What You Find |
|---|---|---|
| Find Quantity | Known price+qty pair + New price | How much quantity you get |
| Find Price | Known price+qty pair + New quantity | How much you pay |
Rate Calculator handles both — just switch between the two modes with one tap.
Formula 1 — Find Unknown Quantity
Use this when you know a price and want to know how much you get:
Known: 800g of chocolate costs ₹350
Question: I have ₹134 — how much chocolate do I get?
✓ For ₹134 you get approximately 305.7 grams of chocolate.
Known: 1kg sugar = ₹40
Question: I have ₹18 — how much sugar do I get?
Formula 2 — Find Unknown Price
Use this when you want a specific quantity and need to know the cost:
Known: 1kg sugar = ₹40
Question: I want exactly 75 grams — how much do I pay?
✓ 75 grams of sugar costs ₹3.
Known: 1 litre petrol = ₹105
Question: I want 2.5 litres — how much do I pay?
Try Rate Calculator Free
No app. No signup. Works on your phone browser instantly.
Calculate any price or quantity in 2 seconds.
Why This Calculation Matters at the Market
In India and around the world, most markets sell goods by weight. The problem is that shopkeepers always quote for full units (1kg, 1 litre, 1 dozen), but customers rarely buy full units. They buy 200g, 75g, 1.5kg, half a litre — and neither party has a quick way to verify the fair price.
This leads to one of three problems:
- Buyers get less than they should for their money
- Sellers accidentally under-charge or overcharge
- Both parties waste time doing mental math that might be wrong
The Rule of Three solves all three problems instantly. And Ratecalc makes it available to anyone with a smartphone — even without doing any math yourself.
Common Units Supported
| Category | Units | Auto-converts |
|---|---|---|
| Weight | g, kg, oz, lb | g → kg at 1000g |
| Volume | ml, L | ml → L at 1000ml |
| Length | cm, m, ft | cm → m at 100cm |
| Count | pcs | — |
10 Currencies Supported
Rate Calculator works for markets worldwide — Indian Rupee (₹), US Dollar ($), Euro (€), British Pound (£), UAE Dirham (AED), Japanese Yen (¥), Bangladeshi Taka (৳), Nigerian Naira (₦), Philippine Peso (₱), and Swedish Krona (Kr).
Do I Need to Download an App?
No. Rate Calculator works entirely in your mobile or desktop browser. Just open the website, bookmark it, or add it to your phone home screen for instant access at the market. It loads in under 1 second and works offline once loaded.
Summary — Rate calculate in 30 Seconds
- Enter the known price and quantity (Step 1)
- Choose: Find Quantity or Find Price (the two tabs)
- Enter your new price or new quantity (Step 2)
- Get the instant answer — with formula shown