What this calculator does
It answers one question: given what you lifted last week and where the sets landed in their rep range, what should the working weight be next week? The answer comes from the same decision BurnX makes when it writes your next week, one lift at a time, so the number here is the number the app would propose.
It is for anyone on a weekly program who adds weight by a rule rather than by feel: double progression, a 12-week block, or a coach's plan with a weekly step.
A worked example
Say your bench press working sets were at 60 kg (132 lb) last week on a barbell. You trained it, every working set reached the top of its 8–12 range, the session did not feel hard, and your last workout was two days ago.
| Step | What applies | Result |
|---|---|---|
| The test | Trained, every set at the top of the range | steps up |
| The step | The larger of 2.5% (1.5 kg) and a plate a side (2.5 kg) | 62.5 kg |
| Cap | At most +20% or +13.6 kg | 72 kg allowed, not reached |
| Rounding | To the plate | 62.5 kg |
Change one input and the answer changes. Sets inside the range but not all at the top: the load holds at 60 kg and the line reads "reach the top of the range first". Sets below the range in a session you rated hard: a little lighter. Lift not trained: 60 kg again, labeled as such. About two weeks away: every lift comes back lighter. On dumbbells the step is the next pair, so a 12 kg press that reached the top of its range goes to 14 kg, not 12.3.
What moves the number
- The rep range. Every working set at the top of its range, with the planned number of sets: the load steps up. Inside the range but short of the top: it holds, and reps are the work. Below the range: it holds, or comes down a little if you rated the session hard.
- The equipment. The step is at least 2.5%, and never smaller than the equipment can make: a plate a side on a bar, the next pair of dumbbells, one pin on a stack. Bodyweight movements have no load to move.
- A lift you did not train. It holds, and the Monday line says why. A lift is never raised on the strength of the other sessions.
- A break. About two weeks without any workout: every lift comes back lighter.
- The deload. Week 12 of a block: lighter loads and fewer sets, nothing else applies.
- The cap. No step may exceed 20% or 30 lb (13.6 kg) above last week's load. One smallest step is always allowed, so light dumbbells still move to the next pair; the cap binds only above that. Decreases are not capped.
- What you logged. In the app next week starts from the load you actually used, not the one on the card. The calculator takes that number as its input. The result is shown in your unit.
Why the top of the range, and not how the week felt
A rep range is a test a set either passes or does not. Eight to twelve means the weight stays until every set reaches twelve; then it goes up and the reps drop back to eight. That is double progression, the oldest sustainable rule in the gym, and it needs no opinion about how the week went. The log already says.
The step is a percentage because a fixed plate treats every lift the same: 2.5 kg is 10% on a 25 kg curl and 1.6% on a 160 kg squat. It is never smaller than a plate because racks cannot make 0.75 kg a side. Past the first months of training, 2.5% a week is about the top of what keeps working, which is why it waits for a week that earned it and why the block ends in a deload rather than compounding on.
Limits of this tool
- It takes one lift at a time. You tell it where the sets landed; the app reads that from the log.
- It does not choose rep ranges or set counts; it moves the load for the sets you already have.
- It does not know the plates your gym owns. The step is the usual one for the equipment; load the nearest thing the rack has.
- Pain, illness and sleep are not inputs. If a weight hurt, the rule is not the thing to consult.
What BurnX does with this number
Every Monday the app writes your next week, runs this decision for every exercise in it, and puts a one-line reason beside each change in the Monday report. The coach can still suggest moving a day, swapping an exercise or changing a load, and you accept or ignore the suggestion, but it cannot go above the same ceiling.