Live-rate context
ETH quotes can differ across exchanges because of liquidity, trading fee tier, app spread and whether you are using simple buy/sell or order-book trading.
What affects the final price
Compare market price, spread, trading fees, withdrawal fees, network choice, liquidity and whether the platform uses app pricing or order-book pricing.
Next step
Use the live calculators, then verify the quote on the exchange before buying, selling or withdrawing funds.