401 lb works out to 4x45 per side plus the bar — call it 405 lb in practice, since gyms rarely stock the odd change. 6 reps sits comfortably inside the 2-to-10 range these formulas were fitted on, so this estimate is about as reliable as the method gets. Your 335 lb set represents about 84% of the estimated max.
How far 401 lb can be trusted
Six reps is where the equations start to separate. The 22 lb between 385 and 407 lb is wider than the same lifter would see from a triple, because past five reps the different curve shapes behind each formula begin to matter. Conditioning also starts to leak into the answer: a six-rep set asks something of your work capacity that a single does not, and lifters who are strong but poorly conditioned come out under-estimated here.
Training loads from a 401 lb max
Programmes are written as percentages of the max, not as absolute weights. From 401 lb, rounded to the nearest 5 lb:
| Percentage | Load | Typical set |
|---|---|---|
| 95% | 380 lb | Heavy single |
| 90% | 360 lb | Doubles and triples |
| 85% | 340 lb | Sets of four to five |
| 80% | 320 lb | Sets of six |
| 75% | 300 lb | Sets of eight |
| 70% | 280 lb | Volume work, ten or more |
401 lb is 4x45 per side plus the bar, 405 lb loaded. At this load the 22 lb the formulas disagree by is bigger than a pair of 10s, which is a good argument for programming off the lower estimate — 385 lb — and letting the bar prove you wrong rather than the other way round. Warm-up jumps also get long here; work up in percentages rather than in fixed plate increments.
The formulas behind this answer, and their limitations
The table above the fold is Epley (1985), Brzycki (1993), Lombardi (1989), O'Conner (1989), Wathan (1994), Lander (1985) and Mayhew (1992), each applied to 335 lb for 6 reps; the headline figure is their median. All seven assume a set taken close to failure with clean technique. At 6 reps you are still inside the fitted band, but conditioning is now affecting the result alongside strength, and the seven have begun to curve away from each other. They also under-rate strong, experienced lifters, who hold a higher percentage of max at any rep count than the regression average. The full account — the populations behind each equation, what a bounced rep does to it, and why we stop at ten reps — is set out on the methodology page. Warm up thoroughly and use safety bars or a spotter before going anywhere near 401 lb. This is a training estimate, not medical advice.