The quickest way of merchanting that I know of. - Buy 1 item that's traded often, you can look these up on the rs site. - Say you buy 1 iron ore for +10% over mid so you can find what it buys for. ie: 350 - Sell that same iron ore for -10% under mid so you can find the selling price. ie: 347 - Flip those numbers and buy whatever amount you want. ie: buy 25k iron ore for 347 - When it's all bought, sell for 350. So 25k (amount you bought) *3 (350-347) = 75k profit. Different items buy and sell at different rates so experiment with some items.