Free calculator
Barbell plate calculator
Tell it what weight you want to lift and it tells you exactly which plates go on each side of the bar. You can tick only the plates your gym actually has, and if the exact weight isn't possible it tells you the closest one that is.
Your bar
What to load per side
Total weight on the bar
100kg
40 kg in plates on each side.
How to load a barbell
The rule is simple, and it's where nearly everyone slips up at the start: the weight you record includes the bar, and the plates are split evenly across both sides. To lift 100 kg on a 20 kg Olympic bar you need 80 kg in plates — that's 40 kg on each side, not 80 per side.
This calculator does that split using the biggest plates first, which is how it's done in practice: fewer plates, more stability and less time wasted between sets.
What each bar weighs
| Bar | Weight | Typical use |
|---|---|---|
| Standard Olympic | 20 kg (44 lb) | Squat, bench press, deadlift |
| Women's Olympic | 15 kg (33 lb) | Women's weightlifting, shorter bars |
| Technique / light bar | 10 kg (22 lb) | Learning technique, warm-ups |
| EZ curl bar | 7-10 kg | Biceps, triceps, accessories |
| American bar (lb) | 45 lb (20.4 kg) | Gyms with imperial equipment |
Check your bar before trusting it. Not every gym bar weighs 20 kg: Smith machines are counterweighted and many end up between 7 and 15 kg effective, and cheap bars in small gyms sometimes sit around 15 kg. A 5 kg error in the bar is a 5 kg error in every log you keep.
Standard plates
In metric, the usual set is 25, 20, 15, 10, 5, 2.5 and 1.25 kg. In pounds, 45, 35, 25, 10, 5 and 2.5 lb. The small plates (1.25 kg and 2.5 kg) are what let you actually progress: a pair of 1.25s adds 2.5 kg to the total, which is the smallest sensible jump on the main lifts.
Why the exact number sometimes isn't possible
With 1.25 kg as your smallest plate, the minimum increment on the bar is 2.5 kg. That means weights like 101 kg or 97 kg simply can't be loaded unless you have fractional plates (0.5 kg or 0.25 kg). When that happens, the calculator tells you how far off you are and what the closest loadable weight is.
Common loading mistakes
- Forgetting the bar. Loading 100 kg in plates and logging 100 kg — you actually lifted 120.
- Loading asymmetrically. One extra plate on a side destabilises the movement and, on bench press, it's dangerous.
- Skipping collars. Tilt the bar and the plates slide; one badly loaded set is all it takes to end up on the floor.
- Assuming the Smith machine bar weighs 20 kg. Almost none of them do, and many don't say.
Frequently asked questions
How many plates do I need for 100 kg?
With a 20 kg Olympic bar: 40 kg per side. The cleanest combination is a 25 kg plate plus a 15 kg plate on each side, or two 20s if you don't have 15s.
Does the bar count towards the total?
Yes, always. When someone says they bench 100 kg they mean the total with the bar included. Recording it any other way makes your logs incomparable with anyone else's — and with your own from another gym.
What about a Smith machine?
It depends on the model: the counterweight reduces the bar's effective weight, usually to somewhere between 7 and 15 kg instead of 20. If your gym doesn't state it, the practical move is to pick a value, note it down and always use the same one so your sets stay comparable to each other.
How do I add weight if the smallest jump is 2.5 kg?
Fractional plates of 0.5 or 1 kg, which allow 1 or 2 kg jumps on the total. They're common on overhead press and bench press, where adding 2.5 kg at once can be too much. The alternative is to progress in reps before adding load.
The same calculator, inside your session
Forge has this built into the workout: it saves your bar and plate setup per exercise, handles cable machines and unilateral movements, and fills in the set weight for you.
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These calculators provide estimates for informational purposes and do not replace the judgement of a qualified training or health professional.