420 lb works out to 4x45 + 1x10 per side plus the bar — call it 425 lb in practice, since gyms rarely stock the odd change. 3 reps sits at the reliable end of the range these formulas were fitted on, so the 31 lb spread here is about as tight as the method gets. Your 385 lb set represents about 92% of the estimated max.
Why 3 reps gives a tight estimate
A triple is close to the best case for this method. The low end of the two-to-ten band is where these regressions were sampled most heavily, and it shows here — the seven land within 31 lb of each other, 7.4% of the estimate, which is small enough that choosing a different formula would not change how you train. If the third rep slowed down but the bar never stalled, 420 lb is a defensible working number.
Training loads from a 420 lb max
Programmes are written as percentages of the max, not as absolute weights. From 420 lb, rounded to the nearest 5 lb:
| Percentage | Load | Typical set |
|---|---|---|
| 95% | 400 lb | Heavy single |
| 90% | 380 lb | Doubles and triples |
| 85% | 355 lb | Sets of four to five |
| 80% | 335 lb | Sets of six |
| 75% | 315 lb | Sets of eight |
| 70% | 295 lb | Volume work, ten or more |
420 lb is 4x45 + 1x10 per side plus the bar, 425 lb loaded. At this load the 31 lb the formulas disagree by is bigger than a pair of 10s, which is a good argument for programming off the lower estimate — 408 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 385 lb for 3 reps; the headline figure is their median. All seven assume a set taken close to failure with clean technique. At 3 reps you are inside the band they were fitted on, so the largest error here is not the equation but judging how close your set really was to failure — three reps left in the tank reads exactly the same to them. 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 420 lb. This is a training estimate, not medical advice.