Fitness Calculators Built for Real Athletes

Epley (1985): Most common, slight overestimate at higher reps.

Brzycki (1993): Most accurate in the 1-10 rep range, validated against 1RM tests.

Lombardi (1989): Power-law formula, accurate for shorter rep ranges.

O'Conner et al (1989): Linear formula, simple and reliable.

Best practice: Use the average of multiple formulas. Accuracy decreases above 6-8 reps because muscular endurance starts contributing more than pure strength.

Cut (40P/35C/25F): High protein preserves muscle while in deficit. Moderate carbs maintain training intensity.

Maintain (30P/40C/30F): Balanced for general health and performance.

Bulk (25P/50C/25F): Higher carbs fuel muscle growth and recovery.

Keto (25P/5C/70F): Very low carb for ketosis. Protein moderate to prevent gluconeogenesis.

Protein minimum: 1.6g/kg for muscle gain, 2.2g/kg when cutting (preserves muscle).

• 5K: 5.0 km / 3.1 miles
• 10K: 10.0 km / 6.2 miles
• Half Marathon: 21.1 km / 13.1 miles
• Marathon: 42.2 km / 26.2 miles

For long-distance races, plan to run slightly slower than your target average pace for the first half, then negative split (faster second half) to avoid the bonk.

VO2 max is the maximum rate your body can consume oxygen during exercise. It is the single best indicator of cardiovascular fitness and a strong predictor of longevity.

Cooper Test: Run/walk as far as possible in 12 minutes on a flat surface. VO2 max = (distance - 504.9) / 44.73

Elite athletes: Marathon runners 70-85, cyclists 75-90, cross-country skiers up to 95+

Average healthy adult: Men 35-45, Women 30-40

MV (Maintenance Volume): Minimum sets to keep current muscle. Around 6-8 sets/week per muscle.

MEV (Minimum Effective Volume): Lowest dose for new growth. 8-12 sets/week.

MAV (Maximum Adaptive Volume): Sweet spot for most lifters. 12-20 sets/week.

MRV (Maximum Recoverable Volume): Most you can recover from. Pushing past this stalls progress.

Based on Dr. Mike Israetel's research at Renaissance Periodization. Numbers vary by muscle group — calves and forearms can handle more, quads and back less.

Olympic plates (kg): 25, 20, 15, 10, 5, 2.5, 1.25, 0.5

Olympic plates (lb): 45, 35, 25, 10, 5, 2.5, 1.25

Standard powerlifting bar is 20 kg / 45 lb. Women's bar is 15 kg / 33 lb. Some training bars are lighter (10 kg / 22 lb).

This calculator uses the largest plates first to minimize plate count loading time.

Predictions use Riegel's formula (1981): T2 = T1 × (D2 / D1)^1.06

The 1.06 exponent reflects the fatigue factor — longer races require disproportionately more time per kilometer than shorter ones.

Important: Predictions assume you have trained appropriately for the distance. Doing well in a 5K does not mean you can run a marathon at predicted pace without specific marathon training.

FTP (Functional Threshold Power) is the maximum power you can sustain for 1 hour. It is the most important metric for cyclists, used to set training zones and measure improvement.

Power-to-Weight Categories (W/kg at FTP):

• Untrained: under 2.0
• Recreational: 2.0-3.0
• Trained: 3.0-4.0
• Strong: 4.0-5.0
• Elite: 5.0-6.0
• World Class: 6.0+

MET = Metabolic Equivalent of Task. 1 MET = energy at rest. Walking at 5 km/h is 3.5 METs (3.5× resting). Sprinting is 23 METs.

Formula: Calories per minute = (MET × 3.5 × weight in kg) / 200

MET values from the Compendium of Physical Activities (Ainsworth et al, 2011). These are averages — actual calorie burn varies by efficiency, terrain, and fitness level.

The Wilks formula adjusts powerlifting totals for body weight, allowing fair comparison across weight classes. Created by Robert Wilks in 1994 and adopted as the IPF standard for ranking lifters until 2020.

Wilks Score Categories:

• 200-300: Recreational
• 300-400: Intermediate
• 400-500: Advanced
• 500+: Elite
• 600+: World Class

The current world records score around 750-850 Wilks. Note: this calculator uses the original 1994 Wilks formula. The IPF now uses GL Points (formerly IPF GL).