If you're using coinbase it's virtually impossible
say you need £150, if you buy £160, it says it will be something like a £4.99 fee, so you'd think "oh i'll have plenty of headroom there, even some spare change" but you won't, once you buy it you'll likely end up with something like £149 in your coinbase balance after they take the purchase fee and whatever the hidden fees are, i've been getting absolutely rinsed by this for 5 years every week
use mempool.space to check the current network fees to send BTC and try to work out a total from there once you've factored in the expected and unexpected fees
i've gotten fairly good at it, usually end up purchasing a couple quid more than i need
so for you, you need £128, safest bet would be to buy £138, minus all the endless fees you'll probably end up with around £131 once it's all said and done which leaves enough to cover network fees to purchase on here!
good luck!
say you need £150, if you buy £160, it says it will be something like a £4.99 fee, so you'd think "oh i'll have plenty of headroom there, even some spare change" but you won't, once you buy it you'll likely end up with something like £149 in your coinbase balance after they take the purchase fee and whatever the hidden fees are, i've been getting absolutely rinsed by this for 5 years every week
use mempool.space to check the current network fees to send BTC and try to work out a total from there once you've factored in the expected and unexpected fees
i've gotten fairly good at it, usually end up purchasing a couple quid more than i need
so for you, you need £128, safest bet would be to buy £138, minus all the endless fees you'll probably end up with around £131 once it's all said and done which leaves enough to cover network fees to purchase on here!
good luck!
