Why exchange rates change a US benchmark expressed in HKD
Follow the three-step conversion from HKD to USD and back, and see how currency movements can change a money-value comparison.
Why is the US index alone not enough?
An amount recorded in HKD and a US index do not share a currency basis. CapsWindow first translates the starting amount into USD, applies the selected US M2 or CPI ratio, and converts the resulting amount back at the ending rate. Therefore the US index can rise while the answer in HKD changes by more or less. That difference includes the exchange-rate effect.
Federal Reserve · H.10: exchange-rate quotation
What is the three-step formula?
Let A be the starting amount, E0 and E1 the starting and ending quotes in HKD per USD, and U0 and U1 the US index values. The result is (A / E0) × (U1 / U0) × E1. In a hypothetical example, A=1,000, E0=10, E1=12 and U1/U0=1.10. The steps are 100 USD, then 110 USD, then 1,320 HKD. The rates are assumptions, not actual quotes for HKD.
| From | Formula | To |
|---|---|---|
| 1000 HKD | 1000 / 10 | 100 USD |
| 100 USD | 100 × 1.10 | 110 USD |
| 110 USD | 110 × 12 | 1320 HKD |
Which details can distort the comparison?
When E rises, one USD costs more HKD: the local currency has weakened against USD. If your source instead quotes USD per local unit, invert the quote before applying this formula. Also align the months. Combining monthly averages is a period comparison, not a reconstruction of an exact daily conversion. Bank spreads, fees and taxes are outside this calculation.
HKD · Data & methodology
Local M2: Official data
Latest observation: 2026-06
Unit: HKD million
How should you compare the four results?
Compare local M2, local CPI, US M2 converted to HKD, and US CPI converted to HKD over the same available period. The US-derived answers do not measure local consumer prices. Read the USD component and the exchange-rate contribution separately before drawing a conclusion. Missing data should lead to an unavailable result, not an invented exchange rate.
Questions & answers
Does a larger converted result mean the US index rose faster?
Not necessarily. A change in HKD per USD can amplify or offset the US index change. Inspect both ratios.
Is this the return from holding dollars?
No. It is a statistical benchmark calculation. It does not model interest earned, trade timing, spreads, fees or taxes.