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View Full Version : Why does a plate at the gym weigh 45 lbs and not 50?


Oedipus
12-02-2014, 12:30 AM
I've read around bodybuilding.com's forum but haven't found a definitive answer yet so I figured the dopers must know. Why does the bigger, standard plate for weight lifting normally weigh 45 lbs instead of just 50? All the other weights are 2.5, 5, 10, and 25... Moreover, why does the standard 7-ft Olympic sized bar weigh 45lbs and not 50? They seem interconnected but for no apparent reason.

Joey P
12-02-2014, 12:41 AM
My WAG is that it's an easy way to get 90 pounds (of plates, not counting the bar), without trying to find 8 10 pound plates and 2 5's or two 25's and four 10's.
Of course, that still makes 80# more work with a 50# weight, so there goes that theory.

Is 100# a magic number to thrive for? It would make it easy to put the 45's on, do that. Put the 2.5's on (95#), then the 5's and you're at a 100 with some baby steps and not having to swap out heavy plates or even having to lift the bar off the ground if that's where it's sitting.

UDS
12-02-2014, 12:42 AM
Olympic standard weight for a barbell is 20 kg, which is just over 44 lbs. Similarly, 20kg is one of the Olympic standard weights. Could the gym be using Olympic standard equipment and simply quoting a rounded value in lbs? Or could the US weightlifting authorities have deliberate;y adopted standards in lbs which are close to the Olympic standards, to make transition to the international events easier for US athletes?

MichaelEmouse
12-02-2014, 12:46 AM
Do the 2.5, 5, 10, 25 and 45lbs plates actually weigh that? Or are they close enough Imperial approximations of metric units, which could put the 45lbs plate at a neat 20 kg?

Telemark
12-02-2014, 07:51 AM
Many (most?) 45 lb plates are labeled 20.4 kg, so they're not the same as a metric plate.

Telperion
12-02-2014, 01:08 PM
Many (most?) 45 lb plates are labeled 20.4 kg, so they're not the same as a metric plate.

There's got to be some thought to it, though. Someone who's used to training with 20 kg plates might not notice an extra pound too much, but six lbs more would probably throw off his technique.

ultrafilter
12-02-2014, 01:50 PM
Rogue, who's one of the big equipment manufacturers, sells plates in pounds (http://www.roguefitness.com/rogue-lb-training-plates) and kilograms (http://www.roguefitness.com/rogue-training-kg-bumper-plates).

AnthonyElite
12-02-2014, 02:25 PM
I think it is because Olympic weight lifting is measured in metric units.

The standard is 20kg, and when it is 44.09lbs it makes sense to round it up to 45lbs in America because we use lbs and 45 is a rounder number than 44. So the plate gets bumped up in kg to compensate.

DrCube
12-02-2014, 03:27 PM
A bunch of weightlifting geeks tried answering this question on another forum I visit (http://startingstrength.com/resources/forum/showthread.php?t=53448).

"Because they already chose 20 kilos in Europe before barbells were ever made in the US" seems to be the consensus. Floor clearance in the case of missed snatches and jerks gives us the 9 inch plate radius. I imagine this sort of thing was worked out for globe barbells before plate loaded barbells were introduced.

JKilez
12-02-2014, 05:43 PM
My understanding was that the bar weighed 45lbs because the old-style collars weighed 2.5lbs each. Why the standard weights are also 45lbs is odd.

DataX
12-02-2014, 05:59 PM
I know nothing about weightlifting, but a check of the rules shows 20 & 25kg plates as standards - and I agree with others that basically are saying - we adopted 45 pounds as it is close enough to 20kg.

Of course they appear really to be 45 pounds - so it isn't like they are saving on stamping/casting these out, but it's close enough for Americans who can't do metric in their head and others that can (who are using the equipment).

Or maybe the guy who first started this - couldn't bench using 50 pounds - so he made 45 ones instead.

Inigo Montoya
12-02-2014, 06:11 PM
Olympic standard weight for a barbell is 20 kg, which is just over 44 lbs.I like it. Plus, if you're used to training with 45 pound thingies, and then go to compete internationally with 44 pound thingies, you can lift more actual thingies than you're used to. I think.

Martin Hyde
12-02-2014, 06:33 PM
Interestingly there isn't a true "standard" for bars or plates. There are certainly standards as promulgated in competition, but out in the field you're going to see wide variation.

For bars there are a huge variety of manufacturers. In fact many/most gyms will be stocked with bars that are slightly out of spec both for Olympic weightlifting and competition powerlifting. You'll see bars a tad longer or shorter than 7.2 ft, bars with diameter from 28-32mm (28mm is the standard for competition.) And with all different kinds of knurling on the actually part of the bar you grip.

These are just covering the bars designed to be somewhat standardized strength training bars. In addition to those there are tons of specialty bars, some that are very thick for specialized training, some that are much shorter, Women's olympic lifting bars etc.

For plates it's actually worth noting serious equipment-enthusiasts also care about what weight a plate is "calibrated" in. You can generally find lb or kg plates, but some are calibrated in opposite weight units to what they are displayed as on the plate. [So if it's printed as 45 lb, it means they may have calibrated it against say, 20.41kg instead of 45 lb.]

Some plates will have both lb and kilos. I've never seen a 20kg plate labeled as 44 lb, but I've seen plenty labeled as 45lb (meaning it's a slight lie on the marking), I've seen a lot of genuine 45 lb plates though, often with a smaller 20.4kg marking on it. I've seen a lot of plates with just pounds or just kilos on them, as well.

In the 70s there were actually a lot of foundries that would pump out plate weights as a small side line. You can still find these plates in gyms even to this day, and they are of extreme variation in accuracy to what's shown on the plate.

RedSwinglineOne
12-02-2014, 07:16 PM
I think Joey P got it right. 45 pounds is just a reasonable increment after 25.

2.5
5
10
25
45

The bigger the difference between available weights, the more smaller weights you need to have on hand to lift an "in-between" amount. 90 pounds would require 2-25s, and 4-10's if a plate was #50.

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