The Landers 1RM Formula

The Landers formula is a widely used method for estimating an individual's one-repetition maximum (1RM) based on submaximal lifts. It originated from a chart attributed to Jeff Landers, published in the National Strength and Conditioning Association Journal (NSCA Journal) in 1985. This overview explores the formula’s origins, mechanics, and practical application in strength training.

Origin

In 1985, the NSCA Journal published a chart titled “Maximum Based on Reps,” attributed to Jeff Landers, a Graduate Assistant at the University of Oregon. Landers later described the chart as a “guesstimated” tool based on observational data gathered informally in the weight room, and noted that it was published without his explicit input or approval. The original chart published in the NSCA Journal can be found here.

The chart provided predicted maximum lift capacities based on the number of repetitions performed at varying intensities, typically from 95% to 75% of 1RM. To allow for easier calculations, a formula was later derived to closely fit the values in the chart:

1RM = (100 × w) / (101.3 - 2.67123 × r)

Where:

• w is the weight lifted
• r is the number of repetitions performed

For example, bench pressing 100 kg for 5 repetitions yields an estimated 1RM of approximately 113.7 kg. The formula is best applied in the 2-10 repetition range, particularly for compound lifts like the squat, deadlift, and bench press.

Misattribution as “McGlothin”

Despite its clear origins, this formula is sometimes incorrectly referred to as the “McGlothin” or “McGlothlin” formula in various online calculators and fitness websites. There is no academic or published evidence linking any researcher by that name to this formula. This mislabeling appears to be the result of confusion or misinformation, as the mathematical form matches the derived equation for Landers' chart exactly. In academic and coaching contexts, the correct attribution remains “Landers.”

Validation and Accuracy

While direct validation studies of the Landers formula itself are limited, the method has been widely used for decades and produces estimates comparable to other established 1RM equations within the 2-10 rep range. It generally performs well for trained individuals and compound movements. A 2002 study reported strong correlations (r > 0.90) for most exercises with 10 or fewer repetitions, though it may overestimate 1RM for exercises like leg press and triceps extension. A 2007 review by Mayhew et al. showed that linear models like Landers perform reliably, with typical correlations (r-values) above 0.90 when compared to actual 1RM tests. However, as with all estimation formulas, accuracy can vary by exercise type, training background, and rep count. For best results, the Landers formula should be used with moderate rep ranges (≤10) and for multi-joint lifts. As with all predictive tools, individual differences should be accounted for, and where possible, estimates should be confirmed through direct testing.

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