Weigh them on a grain scale.

I have a 29" draw, shoot about A 420 grain arrow at aprox. 270 fps. Have yet to have a deer jump my string but believe jumping the string is more to do with noise than speed. I'd rather shoot a quiet bow/arrow at 240 fps than a noisy bow/arrow at 350 fps.
There is also the old standard of fixed blade broad heads vrs, expandables. I was always told fixed blades don't fly well faster than 260 fps. I don't have much trouble at 270.
KE is also A concideration. The fastest lightest arrow you can get wont have the most KE and wont carry KE the best down range where you need it. Like throwing a wiffle ball, doesn't have the weight to carry. A rubber ball the same size you'll be able to throw futher, a lead ball maybe too heavy, have to throw it higher to go further.. You want to find the arrow weight that will give you the best down range KE and accuracy. Many think speed and go too light. That not only hurts down range KE but makes your bow louder. Too heavy and you're shooting rainbows. Checking down range KE is a bit tricky due to you have to measure the speed (fps) down range, to get an accurate number. AT the bow is the easiest way to get FPS but it doesn't tell you what energy is being carried down range. Different vanes, arrow shafts broad heads will all bleed off energy wich can't really be measured 3 feet in front of the bow. I have arrows that get close to the 300 fps mark and at 30 yards they have very little KE left compared to my 420 grain arrows that blow through targets at 30 yards and my bow doesn't make near as much noise with the heavier arrows.I garente deer are more likely to duck my light arrows than my heavy arrows, THE 30 FPS isn't enough speed to put up with the noise.
I saw the difference with a spine shot on a small doe with the 300 fps arrow that burried the broadhead into the backbone with the whole BH hidden inside bone. I spined her because she jumped the string. The same bow, heavier arrow, same bh, I shot A 3 year old buck, in the skull temple to temple, then through the back bone with 2" of shaft clearing the backbone inside the body cavity. . I pinned his head to his backbone until he flopped and broke the arrow. I was planning to spine him, then he reached back and put his head in the same sight line so I took it. right side of head out left side, in left side top of back bone out inside right side of backbone. The buck didn't jump my string, never even blinked,Buck didn't go far. lol Maybe 3 feet sideways. My bow hunting mentor who was an Aluminum arrow fanatic (25+ years) saw what my arrow did and now he's using Axis arrows too from a new bow..