Estimate your 1RM from reps at a given weight.
Free to use, no sign-up required. One-Rep Max is one of 198 tools built into Xenition, alongside a chat that can use them for you.
Estimates the most you could lift for a single rep from a set you have actually done, and turns it into a table of working weights for common rep targets.
Epley: weight × (1 + reps ÷ 30). Brzycki: weight × 36 ÷ (37 − reps). The headline is the average of the two. At exactly 1 rep both equal the weight lifted, since that lift is your 1RM. Training loads invert Epley: load = 1RM ÷ (1 + target reps ÷ 30). Above 12 reps the tool notes that estimates are best at 10 reps or fewer.
80 kg for 5 reps gives 93.3 kg by Epley and 90 kg by Brzycki, so the estimate is 91.7 kg. The table then suggests 83.3 kg (91%) for 3 reps and 68.8 kg (75%) for 10 reps.
They were fitted to different lifters and rep ranges. They agree closely at 10 reps and drift apart below and above it, which is why averaging them is a reasonable middle.
For most people, yes. A true max attempt needs a spotter and good technique, while a hard set of 3 to 6 reps gives a close estimate with less risk.
You do not have to open One-Rep Max to use it. Ask Xenition in plain language and it runs the right tool, then carries the answer into whatever you are working on — a document, a spreadsheet, a deck.