Although quoting (as a guide!) a working percentage value of One Repetition Maximum (1 RM) amongst the www.gymprofessor.com sample weight training gym workout routines, I (GP) would not typically recommend it's use. The reason, most will train suitably for the given repetition range and, in this instance, testing is therefore unnecessary. It also must be considered that, if you are not used to performing low repetition with heavy weight, both psychologically & physically you may not be adapt to perform your 'best' 1 RM, which has resulted in predicted 1 RM (the Brzycki Formula being a common method). However, in certain circumstances - trend analysis, lackluster clients, deconditioned clients - testing 1 RM (or predicted 1 RM), and applying a percentage value for a given number of repetitions, can be sensible.
I have always found that 99% of people performing various fitness tests want to reference (compare) themselves against others or a unit of measure, strength being no different. Hence, below I've listed a commonly used reference chart used against eight commonly performed gym exercises that relate to different muscle groups of the body. The reference chart provides a sensible unit of measure for most levels of fitness. That said, many reference charts have been developed with 'active' people in mind and, therefore, as may be expected anyway, many deconditioned clients are highly likely to achieve the worst scores possible (if a deconditioned client should be performing this fitness test at all).
When testing, it should be factored that some exercises and/ or exercise machines may vary from gym to gym. Likewise, you should factor and/ or make note of any other influencing factors toward either the lift or score for analysis. For example, as the analysis chart below uses bodyweight as a reference, an obese individual may score 'poor', but their main problem is likely to be their bodyweight, rather than their relative strength. Commonsense should be applied to your findings and analysis.
You should take note of the suggested pre-test precautions listed on the Gym Professor website. Notably (in relation to this particular fitness test), the client should have performed relevant stretches and several warm-ups sets prior to attempting their 1 RM. Also, a spotter should be used at all times.
Please CLICK HERE for a printable version of the aforementioned reference chart.