Usually, it's 40%. Although a few brands go much higher, peaking at Stroh's Austrian rum, which is 80% alcohol.
25%
80 proof means it has a 40% alcohol by volume.
Check the label for the 'proof' and divide it in half.
Something 27.5% alcohol by volume would be 55 proof. Cruzan rum is usually this strength.
pirate + alchol = rum
40%
Your question makes no sense the weight of a volume of Rum would depend on how large the volume was.
No. Bacardi has a 151 proof rum, known as an over-proofed rum. 151 Rum has extra alcohol added to the rum to make it more potent and more flammable. 191 proof anything, however, would be almost pure alcohol and would taste like alcohol not rum.
A bottle will usually state it's alcohol by volume (ABV) as "proof" . Proof is double what the percentage of alcohol is. So, a bottle of 60 proof spirits would be 30% alcohol by volume. The highest percentage alcohol in a spirit that I've seen is 151 proof, and that was a bottle of rum.
Even if it says rum. It doesnt meal its "alcoholic" rum. 99% of the food that uses it you put the rum in the sauce while its cooking. Its than lit on fire and the alcohol cooks off. Leaving the flavor of the rum without the alcohol.
200ML spiced rum 35% alcohol
Rum.