The formula
Extra annual cost = Spend × Exposure% × (d ÷ (100 − d))
The d/(100−d) term is the part budgets miss. If your currency loses 10% of its value, one unit buys 10% less foreign currency — so buying the same foreign amount takes 1/(0.9) = 11.1% more local currency. At 20% depreciation the increase is 25%; at 33%, it is 50%. The relationship is convex, which is why severe depreciation years feel disproportionately brutal.
The exposure percentage captures natural protection: spend already held in hard currency, contracts with local-currency pricing, or hedged flows are not exposed. Most importers discover their true exposure share is higher than assumed — local suppliers of imported goods pass depreciation through with a lag, extending exposure beyond direct imports.
How to use this calculator
- 1
Total your foreign-priced annual spend
Direct imports plus local purchases that reprice with the exchange rate — imported goods bought from local distributors count with a lag.
- 2
Estimate the exposed share
Exclude spend already hedged, pre-purchased in hard currency, or contractually fixed in local terms.
- 3
Choose depreciation scenarios
Use your currency’s actual annual history — test the median year and the bad year, not just a comfortable case.
- 4
Feed the result into pricing and budget
The extra cost either compresses margin or enters your prices. Deciding which — and when — before it happens is the entire value of the exercise.
Budget rates and the pass-through decision
Businesses in soft-currency markets set a budget rate — the exchange rate their annual prices assume. The gap between budget rate thinking and reality is timing: depreciation arrives continuously, price reviews arrive quarterly or annually, and margin absorbs the difference in between. The output of this calculator, divided by twelve, is roughly the monthly margin bleed a depreciation scenario causes before the next price review catches up.
Pass-through is also a competitive decision. If competitors import the same goods, deprecation hits everyone and prices generally follow; businesses with local-cost alternatives or long inventory positions can delay pass-through and win share. Knowing your number — and estimating theirs — turns a currency event into a pricing strategy.
Structural defences: harder than hedging, stronger than hoping
Financial hedges cover months; structural defences cover years. The strongest is earning in the currency you spend in — exporters with hard-currency revenue have a natural hedge importers lack. Next best is holding working balances in the buying currency: pre-purchasing your next quarter’s import requirement converts depreciation risk on that spend into an opportunity cost, which is usually cheaper.
Multi-currency account structures make the holding defence operational: collections or converted funds sit in USD or the invoicing currency until suppliers are paid, rather than round-tripping through the local currency twice. KeyBS Pay Global Business Accounts support holding major and African currencies with quote-first conversion when you choose to convert — availability route-dependent.
Common use cases
Annual budgeting
Convert a depreciation assumption into the cost line it actually implies for the year.
Pricing reviews
Size the price adjustment needed to preserve margin under a currency scenario.
Hard-currency balance policy
Compare the cost of holding buying-currency balances against the depreciation they neutralise.
Scenario planning for lenders
Show the measured sensitivity of your cost base to the currency in financing conversations.
Automate this with the API
Track the live indicative rate behind your depreciation scenario.
curl "https://keybs.io/api/v1/tools/fx?from=USD&to=GHS&amount=100000" \ -H "x-api-key: YOUR_FREE_KEY"Free Tools API docs and key registration
Frequently asked questions
Why is the real cost increase bigger than the depreciation percentage?
Because depreciation shrinks the measuring stick. If your currency loses 10% of its value, each unit buys 10% less — so replacing the same foreign purchasing power costs 1/(1−0.10) = 11.1% more. The formula’s d/(100−d) term captures this; at large depreciations the gap becomes dramatic.
How do I estimate my exposed share honestly?
Start with direct foreign-currency invoices — that share is exposed unless hedged. Then add locally purchased goods that are imported upstream: their prices follow the exchange rate with a one-to-three-month lag. Many importers find effective exposure of 60–90% of cost of goods, well above the direct-import share.
Does this apply to appreciation too?
Symmetrically, yes — if your currency strengthens, foreign-priced spend gets cheaper by the mirrored formula. Businesses rarely plan for windfalls, but exporters should: appreciation compresses their competitiveness exactly the way depreciation compresses importer margins.
What depreciation scenario should I test?
Your own currency’s history is the only honest source. Compute the annual change for each of the last ten years and test the median and the worst. Several African currencies have produced both single-digit and 25%+ years within a decade — a budget built on only the median is a plan for half the outcomes.
Is holding USD balances a hedge or speculation?
Holding the currency of your future obligations, sized to those obligations, is hedging — you have pre-purchased known spend. Holding hard currency beyond obligation size is a directional position. The distinction matters for policy and, in some markets, for regulatory treatment of foreign-currency balances.
How does KeyBS Pay fit a depreciation defence?
Two ways: quote-first conversion means each purchase of foreign currency happens at a committed, disclosed rate (fees from 1.5%, route-dependent), and Global Business Accounts let you hold the buying currency once purchased instead of converting twice. Structure first, then rate — the calculator shows what the structure protects.
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