87 lb works out to 2x10 per side plus the bar — call it 85 lb in practice, since gyms rarely stock the odd change. 5 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 75 lb set represents about 86% of the estimated max.
How far 87 lb can be trusted
Five reps is the most common way people estimate a max and the rep count these equations were checked against most often. The seven put your max between 84 and 89 lb. A set of five is short enough that breathing and pacing do not dominate it, so what the bar does on the fifth rep is a fair proxy for what it would do on a single — which is the assumption the whole method rests on.
Training loads from a 87 lb max
Programmes are written as percentages of the max, not as absolute weights. From 87 lb, to the nearest pound, because 5 lb steps collapse into each other at this load:
| Percentage | Load | Typical set |
|---|---|---|
| 95% | 83 lb | Heavy single |
| 90% | 78 lb | Doubles and triples |
| 85% | 74 lb | Sets of four to five |
| 80% | 70 lb | Sets of six |
| 75% | 65 lb | Sets of eight |
| 70% | 61 lb | Volume work, ten or more |
At this end of the rack almost none of those percentages lands on a plate you own. 87 lb itself builds as 2x10 per side plus the bar, which is 85 lb — near enough, and the miss is smaller than the 5 lb the seven formulas disagree by. This is the weight range where a pair of 2.5 lb or 1.25 lb plates genuinely earns its place, because a 10 lb jump here is a much larger proportional step than it is at 300.
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 75 lb for 5 reps; the headline figure is their median. All seven assume a set taken close to failure with clean technique. At 5 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 87 lb. This is a training estimate, not medical advice.