Starting Strength Calculator: Estimate Your Lifts

The Starting Strength calculator estimates your one-rep max (1RM) for the main barbell lifts—squat, bench press, deadlift, and overhead press—based on the weight and reps you can perform. You enter the weight lifted and the number of repetitions completed, and the calculator returns an estimated 1RM along with suggested training percentages. This is a practical tool for lifters following the Starting Strength program or anyone wanting to gauge their strength level without attempting a maximal single.

Formula

The calculator uses the Epley formula, a widely accepted method for estimating one-rep max:

Estimated 1RM = Weight × (1 + Reps / 30)

Where:

• Weight = the load lifted (in pounds or kilograms, as long as you’re consistent)
• Reps = the number of repetitions performed to near failure (typically 1–12)

The formula assumes you are performing the set to technical failure—meaning you could not complete another rep with good form. It is most accurate for rep ranges between 1 and 10, with accuracy decreasing as reps increase beyond that.

Worked Example

Using the default values from the calculator: you squat 225 lb for 5 reps.

1. Divide the reps by 30: 5 / 30 = 0.1667
2. Add 1 to that result: 1 + 0.1667 = 1.1667
3. Multiply by the weight: 225 × 1.1667 = 262.5 lb

The calculator rounds to one decimal place, giving an estimated 1RM of 262.5 lb. The 90% and 80% values are then 236.3 lb and 210.0 lb, respectively.

How the Starting Strength Program Uses 1RM

Starting Strength is a novice barbell program focused on linear progression—adding weight to the bar each session. The program itself does not require you to know your 1RM; you simply start with a weight you can handle for 3 sets of 5 reps and add 5–10 lb each workout. However, a 1RM estimate becomes useful when:

• You want to set up a new cycle or transition to an intermediate program that uses percentages.
• You’re curious where you stand relative to strength standards.
• You need to calculate training loads for accessories or volume work.

Many lifters use the estimated 1RM to set percentages for deload weeks or to compare progress over time. For example, if your estimated squat 1RM is 300 lb, a 70% deload set would be 210 lb for 5 reps.

How to Choose the Right Weight and Reps

For the most accurate estimate, perform a set with a weight you can lift for 2–10 reps with good form, stopping when you could not do another rep. Here are practical guidelines:

• Use a weight you’ve handled before—don’t test with a random load.
• Stop 1–2 reps shy of failure if you’re unsure of your form; the estimate will be slightly conservative but safer.
• Use the same equipment and setup (e.g., same bar, same shoes) for consistency.
• Record the best set from a given day, not a warm-up.

If you only have a 5-rep max, that’s perfect—the formula works well for 5 reps. For higher reps (10+), the estimate becomes less accurate because endurance and fatigue play a larger role. Stick to 12 reps or fewer for the calculator to be meaningful.

Common Mistakes and Limitations

Several pitfalls can skew your 1RM estimate:

• Using a weight that’s too light—if you can easily do 12+ reps, the formula overestimates your true 1RM.
• Not going to near failure—if you stop with 3 reps left in the tank, the estimate will be too low.
• Mixing units—always use the same unit (lb or kg) for weight and result.
• Using the formula for lifts with a long range of motion—like Romanian deadlifts—where rep speed matters more.

The Epley formula is a statistical estimate, not a guarantee. Your actual 1RM could be 5–10% higher or lower depending on your muscle fiber composition, training history, and how well you handle high-intensity singles. It’s a planning tool, not a definitive measurement.

Comparing to Other 1RM Formulas

The Epley formula is one of several. Others include:

• Brzycki: 1RM = Weight × (36 / (37 – Reps))
• Lombardi: 1RM = Weight × Reps^0.10
• O’Conner et al.: 1RM = Weight × (1 + Reps / 40)

For 5 reps, these formulas give similar results—within a few pounds. For example, with 225 lb for 5 reps:

• Epley: 262.5 lb
• Brzycki: 260.7 lb
• Lombardi: 260.0 lb
• O’Conner: 253.1 lb

The differences are small enough that any of them work for planning. The Epley formula is chosen here because it’s simple and widely used in strength training communities.

Safety and Accuracy Tips

Estimating your 1RM is safer than testing a true max, but still take precautions:

• Warm up thoroughly before working sets.
• Use a spotter or safety pins when squatting or benching.
• Never sacrifice form to grind out an extra rep—that’s how injuries happen.
• If you’re new to lifting, consult a coach or experienced lifter for technique guidance.

The calculator assumes you’re using a standard barbell. If you’re using a trap bar or dumbbells, the mechanics differ, so the estimate may be less meaningful. Also, remember that the 1RM estimate is for the specific lift you performed—don’t use your squat estimate to program your deadlift.

Frequently Asked Questions

Is the Epley formula accurate for beginners?

It can be, but beginners often have less consistent technique, which may make the estimate less reliable. As you gain experience and your form stabilizes, the formula becomes more accurate. For novices, it’s better to use a conservative estimate (e.g., round down) to avoid overestimating strength.

Can I use this calculator for accessories like rows or pull-ups?

Yes, but keep in mind that the formula was developed for compound barbell lifts. For bodyweight exercises, you’d need to add your body weight to the load. For dumbbell movements, the estimate is still reasonable if you’re consistent with the rep range.

What if I can only do 1 rep? Is that my true 1RM?

If you perform a single rep with maximal effort, that weight is your true 1RM. The calculator will still give you a value (weight × (1 + 1/30) = weight × 1.033), which is slightly higher than the actual weight. That’s because the formula assumes you could do a few more reps. If you truly did a max single, just use the weight you lifted as your 1RM.

How often should I re-test my estimated 1RM?

Every 4–6 weeks is reasonable for most lifters. If you’re making steady progress on the program, you can update the estimate whenever you hit a new rep PR. Avoid testing too frequently—it can interfere with recovery and progress.

Should I use lb or kg?

Either works, as long as you’re consistent. The formula is unit-agnostic because it’s a multiplicative factor. Most lifters use pounds if they’re in the US, but kilograms are standard in most other places. Just be aware of which unit you’re entering.

Can I use this to plan a 5×5 program?

Yes. If you know your estimated 1RM, you can calculate the weight for 5×5 (typically 80–85% of 1RM). For example, with an estimated 1RM of 300 lb, 80% would be 240 lb. That’s a good starting point for a 5×5 set.

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in w | Weight lifted | lb | 225 | 0 | 2000
in r | Reps performed | reps | 5 | 1 | 12
out e1rm | Estimated 1RM | lb | w * (1 + r / 30) | 1
out p90 | 90% of 1RM | lb | e1rm * 0.9 | 1
out p80 | 80% of 1RM | lb | e1rm * 0.8 | 1