Marginator Arbitrage margin calculator

Find the gap between global crypto prices and South Africa. In one tap.

Crypto trades at one price overseas and another on Luno and VALR. Marginator pulls live prices from seven exchanges, runs every possible route and shows you which one pays, in about a second.

Role: Design and build
Platforms: iPhone and Apple Watch
Year: 2026

React Native
Expo
TypeScript
SwiftUI
watchOS
Live market data

The Marginator app icon: a gold M coin on a white tile

Marginator on iPhone: R100,000 in rand, dollar, Bitcoin, Binance and Luno selected, with Check and Optimise buttons

Potential Profit

R 2,412.00

+2.41%

⚡ Best of 90 routes tested

02 / The idea

Same coin. Different price.

Buy where it is cheaper, sell where it is dearer, keep the difference. Marginator works out whether the gap is worth it before you move a cent.

RYour randR100,000
$Convertone FX hop
Buy a coinBTC, ETH or XRP
Abroadcheaper
Sell in SAdearer
+Keep the gap+2.41%

Example figures. Before fees and slippage.

The Marginator calculator screen with its five choices and the Check button numbered 1 to 6

03 / How it works

Five choices. One answer.

1R
How muchAny amount in rand, dollars, euros or pounds.
2$
Buy withThe currency you buy in abroad. Converted once, at the live rate.
3
Which coinBitcoin, Ether or XRP.
4
Buy abroadBinance, Kraken, Coinbase, Gemini or Bitstamp.
5
Sell at homeLuno or VALR, in rand.
6Check
CheckOne tap for the profit and margin, before fees.

04 / Optimise

Every route. Live. In a second.

Not sure which coin, exchange or currency gives the best margin? Tap Optimise. Marginator prices every combination on live data and hands you the winner.

1Tap Optimise
From the screen you already know.
2Every route, priced
Live prices from seven exchanges, every combination tested.
3The winner, loaded
Profit, margin and the exact route.
4Or see all 90, ranked
Tap any route to load it.

$€£

3 currencies

3 coins

5 global exchanges

2 SA exchanges

90 routes

priced live, in about a second

05 / Live data

Straight from the source.

The moment the app opens, it connects to every exchange and the currency feeds at once. Each icon lights up as its prices land. Fresh prices load again every minute.

Binance, Kraken, Coinbase, Gemini, BitstampConnected
Luno and VALRConnected
$Live rand exchange ratesConnected
An exchange goes quiet?Greyed out, app carries on

The Marginator splash screen: exchange icons lighting up, 7 of 8 sources connected, above a gold M coin

06 / Three ways in

Start where you are.

Start with cash, start with crypto you already hold, or flip the whole trade around. Two tick boxes switch the flow. The answer stays one tap away.

Cash
Start with rand, dollars, euros or pounds.
R$R
Crypto
Already hold coins overseas? Sell here, or swap first if it pays.
R
Flip flow New
Run it backwards: buy on Luno or VALR, sell abroad, bring it home.
R$R