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One rep max calculator

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Every formula here is published and cited, and the arithmetic is shown on the page. How we know this.

Short answer

Enter a weight and the reps you got with it. This one rep max calculator runs four published formulas and shows all four, because they disagree and your max is a range, not a number.

Units
lb

Clean reps to near-failure. Grinders and half reps wreck the estimate.

253.1lb

Lowest estimate

258.3lb

Midpoint of the four

264.3lb

Highest estimate

Four published formulas, 11 lb apart. That spread is the point. Treat your max as a range, program off the low end, and go test a real single when you want the real number.

One-rep-max estimates from four published formulas
FormulaEquationEstimated 1RM
Epley1RM = w x (1 + r / 30)262.5 lb
Brzycki1RM = w x 36 / (37 - r)253.1 lb
Lombardi1RM = w x r^0.10264.3 lb
O'Conner1RM = w x (1 + 0.025 x r)253.1 lb

Where these equations come from

  • Epley: Epley, B. (1985). "Poundage Chart." Boyd Epley Workout. Lincoln, NE: Body Enterprises.
  • Brzycki: Brzycki, M. (1993). "Strength Testing — Predicting a One-Rep Max from Reps-to-Fatigue." Journal of Physical Education, Recreation & Dance, 64(1), 88-90.
  • Lombardi: Lombardi, V. P. (1989). Beginning Weight Training: The Safe and Effective Way. Dubuque, IA: Wm. C. Brown.
  • O'Conner: O'Conner, B., Simmons, J., & O'Shea, P. (1989). Weight Training Today. St. Paul, MN: West Publishing.

Training weights off the midpoint

Derived by inverting the Epley equation — solve w = 1RM / (1 + r/30) for each rep count.

RepsWeight% of 1RM
1250 lb96.8%
2242.2 lb93.8%
3234.8 lb90.9%
4227.9 lb88.2%
5221.4 lb85.7%
6215.3 lb83.4%
7209.4 lb81.1%
8203.9 lb78.9%
9198.7 lb76.9%
10193.7 lb75%

Gear that fits the math

If you are going to actually test a max

An estimate is an estimate. If you plan to find out for real, the thing that matters is what catches the bar when the rep does not go up.

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Safeties, no spotter

ULTRA FUEGO Multi-Functional Power Cage

B0BFQVVFB7
Power racksULTRA FUEGOJ-hooks, dip handles, landmine attachment
Includes
J-hooks, dip handles, landmine attachment
Optional
Cable pulley system

Best for: A first rack that covers squats, presses, dips and landmine work.

Skip if: You need Westside 1 in hole spacing through the bench zone — check before ordering.

Check these yourself before ordering

  • — Ceiling height and footprint
  • — Hole spacing in the bench and squat zone
  • — Whether the pulley system is included in the option you picked
View on Amazon

Specs read from the listing on 2026-07-24. Listings change — confirm the current spec and option before you order.

Flat and incline

HANDBODE Adjustable Weight Bench

B0CH5HJWYY
BenchesHANDBODE1,500 lb
Capacity
1,500 lb
Positions
Incline, upright and flat

Best for: Full-body pressing work including seated overhead at the upright setting.

Skip if: You only ever bench flat — a dedicated flat bench is more stable and cheaper.

Check these yourself before ordering

  • — Pad height at flat
  • — Gap between seat and back pad at incline
  • — Footprint against your rack
View on Amazon

Specs read from the listing on 2026-07-24. Listings change — confirm the current spec and option before you order.

Fixed bar path

DONOW Smith Machine with Weight Stacks

B0D632P2SW
Smith machinesDONOW352 lb weight stacks
Weight Stacks
352 lb weight stacks
Cable Ratio
2:1 cable crossover
Frame
2 in x 2 in steel
Smith Bar
Linear-bearing Smith bar
Pulleys
Aluminium pulleys (listed as optional)
Extras
Power rack, lat pulldown

Best for: One corner of a garage doing Smith work, cable crossover and rack work without three separate machines.

Skip if: You want free-weight barbell work. A Smith bar runs on rails.

Check these yourself before ordering

  • — Ceiling height and full assembled footprint before ordering
  • — Which options the listing includes — the pulleys are listed as optional
  • — The counterbalanced Smith bar weight, which is not 45 lb
View on Amazon

Specs read from the listing on 2026-07-24. Listings change — confirm the current spec and option before you order.

The four formulas and where they come from

These are real published equations, reproduced as published. Nothing here was tuned, averaged, or invented.

Epley

1RM = w x (1 + r / 30)

Epley, B. (1985). "Poundage Chart." Boyd Epley Workout. Lincoln, NE: Body Enterprises.

Considered reliable to about 10 reps.

Brzycki

1RM = w x 36 / (37 - r)

Brzycki, M. (1993). "Strength Testing — Predicting a One-Rep Max from Reps-to-Fatigue." Journal of Physical Education, Recreation & Dance, 64(1), 88-90.

Considered reliable to about 10 reps.

Lombardi

1RM = w x r^0.10

Lombardi, V. P. (1989). Beginning Weight Training: The Safe and Effective Way. Dubuque, IA: Wm. C. Brown.

Considered reliable to about 12 reps.

O'Conner

1RM = w x (1 + 0.025 x r)

O'Conner, B., Simmons, J., & O'Shea, P. (1989). Weight Training Today. St. Paul, MN: West Publishing.

Considered reliable to about 10 reps.

In the equations, w is the weight you lifted and r is the number of reps you completed with it.

A worked example: 225 lb for 5

Here is every formula run by hand on the same set, so you can check our arithmetic.

One rep max estimates for 225 lb lifted 5 times
FormulaSubstitutedEstimate
Epley225 x (1 + 5/30) = 225 x 1.1667262.5 lb
Brzycki225 x 36 / (37 − 5) = 8100 / 32253.1 lb
Lombardi225 x 5^0.10 = 225 x 1.1746264.3 lb
O’Conner225 x (1 + 0.025 x 5) = 225 x 1.125253.1 lb

Spread: 253.1 lb to 264.3 lb — about 11 lb between the lowest and highest published answer for the exact same set. Any site that hands you one number is hiding that gap.

Using the number without lying to yourself

An estimated max is a programming tool. It is the input to your percentages, not a line on your record. If your program says 80 percent for triples, run 80 percent off the low end of the range and you will be training at a weight you can actually handle for the volume prescribed.

Two things wreck an estimate faster than anything else. The first is rep quality: if the last two were half reps with a bounce, you did not do that many reps at that weight. The second is rep count: the further you get from a heavy triple, the more the estimate measures your conditioning instead of your strength.

Then load the bar

Once you have a training weight, the warm-up set generator will build the ramp to it and the plate math calculator will tell you what goes on each side. Both round to weights your plates can actually make.

Equipment by category

Looking for the gear itself?

Every piece of equipment we have spec’d, split by what it is. Each page compares the same published numbers side by side — no prices, no ratings, nothing we pretend to have tested.

Questions people actually ask

▶How accurate is a one-rep max calculator?

It is an estimate, and the formulas disagree with each other by a meaningful margin. At 225 lb for 5 reps the four equations on this page span roughly 11 lb. Accuracy drops as reps climb, because a set of 12 depends far more on conditioning and pain tolerance than a set of 3 does. Treat the output as a range.

▶Which 1RM formula is the best one?

There is no single best one, which is why this calculator refuses to pick. Brzycki and O’Conner tend to read lower, Epley and Lombardi higher. Programming off the low end of the range is the conservative choice and the one that keeps you off the platform floor.

▶How many reps should I use for the estimate?

Fewer is better. A set of 3 to 5 taken close to failure gives the tightest estimate. Every formula here degrades past about 10 reps, and the calculator flags each one when you go beyond the range its published source covers.

▶Do I have to lift to failure?

The formulas assume a set taken to or very near failure with clean reps. If you left three in the tank, the estimate is low. If your last two reps were grinding half reps, the estimate is high. Garbage in, garbage out.

▶Is estimating a max safer than testing one?

It avoids the risk of a maximal attempt, which is why coaches use it. It does not replace a tested max if you need a real number for a meet. This is not medical advice — if you have any doubt about heavy loading, talk to a professional who can see you lift.