Currency Mental Math Cheat Sheet

10: AED, CAD, CHF, GBP, JPY, MYR, NPR, SGD, USD, VND. Pick one at the top of the tool; the page link updates (for example ?v=inr-aed) so you can bookmark or share that exact view.

Add a zero, multiply by 7 and divide by 3 — that is the fraction 70/3, or about ₹23.33 per dirham, and at a rate near ₹23.4 it lands under 0.3% from the exact answer. AED 300 becomes 3,000, then 21,000, then ₹7,000 against an exact ₹7,020. If dividing by 3 is awkward, multiply by 22.5 instead and accept being about 4% low.

Round the rate to a whole number and multiply. At roughly ₹62 per dollar the quick rule is to multiply by 60, which lands about 3% low, then add 2.5% — around ₹1.50 in every ₹60 — if you want to close most of that gap. Enter the day's rate above and the sheet picks the closest easy rule for it.

Add two zeros, then adjust. At around ₹107 per franc, CHF 45 becomes 4,500 plus about 5% — roughly ₹4,725, against an exact ₹4,815. Enter the day's rate above and the sheet recalculates the nudge for it.

Multiply by 100 and then add an eighth. At a rate near ₹112 to the pound that rule gives ₹112.5 and lands under half a percent from the exact answer, which is far better than simply multiplying by 100 — that alone is nearly 11% low. Adding an eighth is easy because it is half of a quarter: £60 becomes 6,000, then 6,000 + 750 = ₹6,750.

Drop a zero and then take a bit over half. At a rate near ₹0.57 to the yen, dropping a zero and multiplying by 5.5 gives ₹0.55 per yen and lands about 3.5% low; adding 2.5% to that result brings it inside about 1%. So ¥3,000 becomes 300, then 1,650, then about ₹1,690 against an exact ₹1,710.

Multiply by 20 and add a little. At a rate near Rs 20.5 per ringgit, multiplying by 20 lands 2.4% low, and adding 2.5% — roughly Rs 2.50 on every Rs 100 — makes it exact. So RM 12 is 12 × 20 = 240, plus about 6, which is Rs 246. Enter today's rate and the tool recalculates the multiplier and the nudge for it.

NPR 1.60 to INR 1, a peg Nepal Rastra Bank has maintained since 12 February 1993. So ₹1,000 is NRs 1,600, and NRs 1,000 is ₹625.

Multiply by the rate rounded down to the nearest 5 and then add a small nudge. At a rate near ₹66 to the Singapore dollar, multiplying by 65 and adding 2.5% lands under 1% from the exact answer, while multiplying by 65 alone is about 1.5% low — fine for a hawker meal, less so for a S$1,500 phone. Round up to 70 instead if you would rather over-estimate.

Round the rate to the nearest half or whole number and multiply. At ₹86 to the dollar, multiplying by 85 is the cleanest rule and lands about 1.2% low — on a $100 purchase that is a ₹100 error, which is fine for deciding whether to buy. Round the other way and multiply by 90 if you would rather over-estimate than be surprised by the card statement.

Drop three zeros from the price, then multiply by a small number. At roughly ₹0.0034 per dong, drop three zeros and multiply by 3.5 — so 60,000₫ becomes 60 × 3.5 ≈ ₹210, against an exact ₹204. Enter the day's rate above and the sheet recalculates the multiplier for it.