What this calculator does
It turns the weight you want to lift into the plates to put on each side of the bar. You choose the bar, 20 kg or 15 kg (45 lb or 35 lb), and the plates you have. It subtracts the bar, halves what is left and fills that half heaviest plate first, which is how the fewest plates end up on each sleeve.
It is for anyone who has stood at a loaded bar doing the subtraction in their head between sets, and for anyone training in a gym with an incomplete rack. When the exact weight cannot be made from the plates you listed, it says so and gives the nearest weight that can.
A worked example
A 20 kg bar, a full rack.
| Target | Minus the bar | Per side | Plates per side |
|---|---|---|---|
| 100 kg (220 lb) | 80 kg | 40 kg | 20 + 20 |
| 87.5 kg | 67.5 kg | 33.75 kg | 25 + 5 + 2.5 + 1.25 |
| 62.5 kg | 42.5 kg | 21.25 kg | 20 + 1.25 |
| 86 kg | 66 kg | 33 kg | cannot be loaded; nearest 85 kg: 25 + 5 + 2.5 |
The 87.5 kg row is why the arithmetic is worth seeing once on a page: 87.5 minus 20 is 67.5, half of that is 33.75, and 33.75 is a 25, a 5, a 2.5 and a 1.25. If the 25s are taken, 20 + 10 + 2.5 + 1.25 is the same 33.75. The common mistake is in the smallest plate: one 1.25 on each side adds 2.5 kg to the bar, not 1.25. In pounds the first two rows read 225 lb = 45 lb bar + 45 + 45 per side, and 185 lb = bar + 45 + 25 per side.
How plates round
The smallest plate on the rack sets the step the bar can move in. With 1.25 kg plates a pair adds 2.5 kg, so any weight that is the bar plus a multiple of 2.5 kg can be loaded: 22.5, 25, 27.5 and so on. With 2.5 lb plates the step is 5 lb. Take the 1.25s away and the step doubles to 5 kg; a rack with only 5s and 10s moves in 10 kg steps, and 87.5 kg becomes 80 or 90.
When the weight you typed is not on that ladder, the calculator returns the nearest rung and says so under the result, so you can decide whether to take the lighter or the heavier side of it.
The hotel preset
Hotel and apartment gyms usually have one bar and a short set of plates: 1.25, 2.5, 5 and 10 kg (2.5, 5, 10 and 25 lb), often two or four of each. The hotel preset uses only those sizes. Any weight a full rack can load, this one can too, as long as there are enough 10s: 100 kg is the bar plus four 10s a side, eight plates in all, which is more than most hotel racks hold.
The preset does not count your plates; it assumes you have enough of each size. If the rack has four 10s, enter the sizes under Custom and treat 60 kg as the ceiling for the bar: 20 + 2 × (10 + 10). Above that, the honest answer for the week is more reps at the weight the rack allows, or the dumbbell version of the lift.
Limits of this tool
- It assumes unlimited plates of each size. Racks run out of 20s on a busy evening; the per-side list is the fewest plates, not the only combination.
- It does not weigh your bar. Not every bar is 20 kg: women's and training bars are 15 kg, technique bars are lighter, and the weight is rarely written on the sleeve. If the total feels wrong, the bar is the first suspect.
- Collars are not included. Spring collars weigh almost nothing; competition collars are 2.5 kg each.
- Dumbbells and machines are outside its scope: a fixed dumbbell is one number, and a stack moves by its pins.
What BurnX does with this
In the app the session screen shows the day's working weight in your unit, set the Monday before from what you lifted. Loading the bar is yours; this calculator is the same subtraction on a page, so it works for any program and any rack.