# GHS–USD: QASH reference calculation

A worked calculation of the common-reference relationship using explicitly supplied QASH reference values. The preset figures are illustrative; operational values require a current authorized publication.

## Publication status
Published by the OpenForex Society, the standard-setting core of the OpenForex Foundation, as part of its established standards service to the open standards community.

## Version
0.3.0

## Last Updated
2026-10-23

## Inputs and scope
How can an amount in one instrument be expressed in another when both already have values against the same reference unit?

The QASH symbol denotes the QASH reference unit. Both reference values in the calculation use one common scale and one stated input set. Fees, spreads and slippage are handled separately by an executing service. Decimal arithmetic preserves the specified numeric policy.

| Input | Reference example | Meaning |
| --- | --- | --- |
| Source amount | 120.00 GHS | Amount to translate |
| GHS reference value | 0.50 QASH per GHS | QASH units for one GHS |
| USD reference value | 6.00 QASH per USD | QASH units for one USD |
| Output policy | Two decimal places | Round only final output, half-up |

## Calculation
First express the source amount in QASH:

**120.00 GHS x 0.50 QASH/GHS = 60.00 QASH**

Then divide by the reference value of one USD:

**60.00 QASH / 6.00 QASH/USD = 10.00 USD**

Units cancel at each step. The calculated amount is 10.00 USD under the stated reference values and output policy.

## Consistency checks
Reversing these inputs without fees gives 10.00 USD times 6.00 QASH/USD, divided by 0.50 QASH/GHS, or 120.00 GHS. This exact reversal follows from these numbers; it is not a general promise of lossless conversion after rounding.

If the USD reference value changes to 8.00 QASH/USD while other inputs stay fixed, the output becomes 7.50 USD. This demonstrates sensitivity to supplied reference values. It does not explain how those values should be determined.

## Invalid cases
A zero USD denominator makes the calculation undefined and must fail. Missing quote direction makes interpretation ambiguous. A negative reference price is outside this example's domain. Mixed snapshots require a separate policy.

## Using authorized reference values
For operational use, obtain both reference values from the same QASH Valuation Authority publication. Preserve the epoch, reference direction, methodology version, observation version, validity period and integrity signature. The [authority publication status](/governance/valuation-status.json) identifies current availability; the [reference calculator](?page=lab) records the values entered and their provenance.

See the [TVX standard](?page=seed-content/tvx-formula/1.0.0), [simulation methods](?page=seed-content/simulations/index), and [QASH overview](?page=seed-content/qash/overview).