If your computer is a 64 bit PC that means you can use more than 4gb of ram which will allow Minecraft to use more ram.
A lot of people mistakenly install the 32 version of Java which doesn't allow Minecraft to run like it should.
So you'll want to open up computer properties and check if you have a 64 bit machine. An easier way to tell is if your computer has more than 4gb of ram. If it does then you own a 64 bit PC.
Check your java version and make sure it's 64 bit. Hope this trick helps!