377 lb works out to 3x45 + 1x25 + 1x5 per side plus the bar — call it 375 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 315 lb set represents about 84% of the estimated max.
How far 377 lb can be trusted
Six reps is where the equations start to separate. The 21 lb between 362 and 383 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 377 lb max
Programmes are written as percentages of the max, not as absolute weights. From 377 lb, rounded to the nearest 5 lb:
| Percentage | Load | Typical set |
|---|---|---|
| 95% | 360 lb | Heavy single |
| 90% | 340 lb | Doubles and triples |
| 85% | 320 lb | Sets of four to five |
| 80% | 300 lb | Sets of six |
| 75% | 285 lb | Sets of eight |
| 70% | 265 lb | Volume work, ten or more |
377 lb is 3x45 + 1x25 + 1x5 per side plus the bar, 375 lb loaded. At this load the 21 lb the formulas disagree by is bigger than a pair of 10s, which is a good argument for programming off the lower estimate — 362 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 315 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 377 lb. This is a training estimate, not medical advice.