All five strength calculators
1RM estimation, training percentages, and plate loading — the math most strength programs run on. Every calculator surfaces its inputs, reliability framing, and where the published guidance ends and StrengthMath methodology begins.
One rep max calculator
→Estimate 1RM from a submax set using all four published prediction formulas (Epley, Brzycki, Lombardi, O'Conner) plus a cross-formula average. Reliability bands per LeSuer 1997.
Output: Headline 1RM + per-formula breakdown + ±confidence band
Sources: Formulas reproduced from original publications. Reliability bands (HIGH ≤5 reps / MEDIUM 6–10 / NOISY 11–15 / VERY NOISY 16+) are StrengthMath methodology grounded in LeSuer 1997 directional findings, labeled as such.
Incline bench 1RM calculator
→Same four-formula engine as the general 1RM calculator, framed for incline bench specifically. Most lifters press 70–85% of flat bench on a 30° incline.
Output: Incline bench 1RM + reliability band + incline-vs-flat context
Sources: Math identical to flat bench (formulas don't know which lift you did). The 70–85% incline:flat ratio is a population-level observation, not a conversion factor.
Dumbbell bench 1RM calculator
→Per-dumbbell 1RM and total external load. A wide barbell-equivalent range is available behind a toggle — there's no consensus conversion factor between implements.
Output: Per-dumbbell 1RM (PRIMARY) + total external load + rough barbell range (SECONDARY, behind toggle)
Sources: 1RM formulas same as barbell. The 1.05–1.25× barbell-equivalent range is StrengthMath methodology — practitioner-consensus framing reflecting stability, ROM, angle, increment, and technique differences.
Percentage of 1RM calculator
→Load table from 50% to 100% of 1RM with NSCA traditional band highlighted, ACSM 2026 updates flagged where they differ. Sets/reps + RIR target per goal.
Output: Goal band + sets/reps + RIR target + 50–100% load table
Sources: NSCA bands from 'Essentials of Strength Training and Conditioning' (4th ed.). ACSM 2026 updates from the 2026 Position Stand on Resistance Training. Both framings surfaced; calculator highlights NSCA traditional in-table because it's the field-default for written programs.
Plate calculator
→Per-side plate loadout for any target weight. Defaults to IPF/USAW kg plates and US commercial lb plates. Customizable bar weight (20 kg / 45 lb / 15 kg women's / custom).
Output: Per-side plate combination + achieved total + bar
Sources: kg ↔ lb uses 1 kg = 2.2046226218 lb (NIST SP 811). Plate sets and bar weights are conventional gym inventories. Greedy descending algorithm is provably optimal for both standard plate sets.
About these calculators
Engines live in lib/strength/ and are 100% test-covered — every published formula and band is reproduced from its source and verified against worked examples. The methodology page covers the full sourcing posture, what each calculator does NOT model (injury, technique, ROM, equipment, fatigue, coaching), and the specific places where StrengthMath methodology fills a gap the published literature leaves.