Methodology

Every number on GainsMath comes from a published formula or table. This page lists them, says how the implementation was checked, and names the choices we made where sources leave room.

How the calculators were checked

Each formula is implemented once and covered by automated tests. The expected values in those tests come from the source itself (worked examples in federation documents, official coefficient tables, spreadsheets published by the federation) or from an independent recalculation of the published formula. Where a federation publishes a full table, the implementation was compared with it cell by cell.

One-rep max estimates

Seven equations: Epley, Brzycki, Lander, Lombardi, Mayhew et al., O'Connor et al. and Wathen. The equations were taken from two peer-reviewed comparisons that print them (Reynolds et al. 2006; Mayhew et al. 2008), because several of the original books are out of print.

• Epley is written as weight × (1 + reps / 30). Published versions also show 0.033 and 0.0333 as the multiplier; they are rounded forms of 1/30.
• The default result is the average of the equations that are defined for the entered reps. You can pick a single equation instead.
• Rep input is limited to 10. Reynolds et al. list 10 reps as the upper limit for Epley and Brzycki.
• For 1 rep the result is the weight itself. Most equations return slightly more than the weight at 1 rep (Epley gives 1.033 × weight), which is not meaningful for a single.

RPE and reps in reserve

The RPE chart is the Reactive Training Systems chart published by Mike Tuchscherer (RPE 6.5 to 10, 1 to 12 reps). The reps-in-reserve reading of RPE (RPE 10 = no reps left, RPE 9 = one rep left) follows Zourdos et al. 2016.

Powerlifting scores

• DOTS: coefficients from the formula's author, Tim Konertz, checked against the IPF's 2020 evaluation report.
• Wilks (original) and Wilks 2020: the polynomials reproduce all 5,440 cells of the Powerlifting Australia tables to four decimals, and 2,761 of the 2,770 cells of the IPF Wilks table (the other 9 differ only in how an exact half was rounded). Below 40 kg bodyweight neither gives a score. Above the last row of the IPF's original table (205.9 kg for men, 150.9 kg for women) the original Wilks keeps that row's coefficient, as the table itself states; Wilks 2020 gives no score above its tables (200.95 kg for men, 150.95 kg for women).
• IPF GL points: the eight coefficient sets in the IPF document "The IPF GL Coefficients for Relative Scoring" (May 2020), with the coefficient rounded to six decimals as in the IPF's own spreadsheet.
• Age adjustment: Foster (ages 14–23) and McCulloch (ages 40–90) coefficients as published by USA Powerlifting. USAPL uses them with Wilks. DOTS and IPF GL have no official age adjustment; where we offer one, the page says so.
• Not published: a Glossbrenner calculator. Its official definition is a lookup table that contains typesetting errors and does not match a federation results file above 125 kg, so we could not verify it.

Plates, warm-ups and programs

• Kilogram plates, bar and collar weights follow the IPF Technical Rulebook (2026). Pound plate sets are the common 45/35/25/10/5/2.5 lb set; there is no federation standard for them, so you can change the set.
• The 5/3/1 calculator uses the percentages and training max described by Jim Wendler (90% by default, 85% as an option).
• The warm-up calculator's default is the even-jump rule from the Starting Strength FAQ: empty bar, then even jumps up to the work weight. You can also enter your own percentages.

Units and rounding

One pound is exactly 0.45359237 kg (NIST Handbook 44, Appendix C). Scores are calculated in kilograms; pound inputs are converted first. Training loads are rounded to the nearest 5 lb or 2.5 kg unless a page lets you change the increment.

What we do not publish yet

Strength standards ("how strong am I") need a large, verifiable dataset of lifts. Until such data is in place, the site shows no strength levels.

Sources

1. Reynolds JM, Gordon TJ, Robergs RA. Prediction of one repetition maximum strength from multiple repetition maximum testing and anthropometry. J Strength Cond Res. 2006;20(3):584–592.
2. Mayhew JL, Johnson BD, LaMonte MJ, Lauber D, Kemmler W. Accuracy of prediction equations for determining one repetition maximum bench press in women before and after resistance training. J Strength Cond Res. 2008;22(5):1570–1577.
3. Tuchscherer M / Reactive Training Systems. Customizing Your RPE Chart (2016).
4. Zourdos MC et al. Novel Resistance Training–Specific Rating of Perceived Exertion Scale Measuring Repetitions in Reserve. J Strength Cond Res. 2016;30(1):267–275.
5. Konertz T. Die DOTS-Formeln.
6. International Powerlifting Federation. The IPF GL Coefficients for Relative Scoring (2020).
7. Powerlifting Australia. Wilks formula tables.
8. USA Powerlifting. Age Coefficients Used in USA Powerlifting (2012).
9. International Powerlifting Federation. Technical Rulebook (effective 1 March 2026).
10. Wendler J. 5/3/1: How to Build Pure Strength.
11. National Institute of Standards and Technology. Handbook 44 (2026), Appendix C.