Brad Frost has put together a great tool for creating performance budgets on Codepen and is up there and ready for you to use on your next (or current) project.
I thought this was so cool that I’ve added it to the resources section.
The Performance Budget builder lets you lay out your template types, set a size budget for each template type, then plug in the sizes for each asset category that will load in the template. The tool will adjust each category’s width accordingly and yell at you if you exceed your budget. Pretty fun! Fair warning, this is mostly an experiment and hasn’t been cross-browser tested or anything like that. Feel free to take it and run with it.An excerpt from Performance Budget Builder