Calculators for coaches
The numbers behind the training and the coaching business, worked out with the formula in plain sight.
Each calculator ships the formula explained, a table of precomputed values and the assumptions it runs on, so you can check the result or do the arithmetic by hand. Some calculators answer the programming: loads, sets, paces and zones. The rest answer the business: price, capacity, revenue and what a client is worth.
12 calculators
How much to charge per session
The formula
Price per session = (Target income + Fixed costs) ÷ (Sessions per month × (1 − Deductions))
The price you need to charge per session comes from dividing what you want to earn plus your fixed costs by the sessions you bill each month, adjusted for what tax and payment fees take. With a target of 2,000 a month, 300 in fixed costs, 60 sessions and 25% in deductions, the price is 51 per session. Fewer sessions raise the price in the same proportion.
How many clients you can handle
The formula
Capacity = Weekly hours ÷ ((Sessions per week × Duration) + Admin hours per client)
The number of clients you can handle comes from dividing your weekly hours of client work by what each client costs you per week, counting sessions and also programming, messages and check-ins. With 30 weekly hours, two one-hour sessions per client and two hours of admin, capacity is 7 clients. Admin hours weigh more than sessions do.
What you will bill twelve months from now
The formula
Steady roster = New clients per month ÷ Monthly dropout rate · Revenue = Roster × Monthly fee
A client roster stops growing when arrivals match departures, so the ceiling is new clients per month divided by the monthly dropout rate. With 4 new clients a month and 10% dropping out, the roster settles at 40 clients, no matter how many you start with. At a fee of 80, that is 3,200 a month.
What a client is worth in total
The formula
Lifetime value = Monthly fee ÷ Monthly dropout rate · Average stay = 1 ÷ Dropout rate
A client's lifetime value is their monthly fee divided by the monthly dropout rate, because a 10% dropout rate equals an average stay of 10 months. At a fee of 80 and 10% dropout, each client is worth 800 across the relationship. Halving dropouts doubles that figure without touching the price.
What is your estimated 1RM?
The formula
Epley: 1RM = weight × (1 + reps / 30). Brzycki: 1RM = weight × 36 / (37 − reps). The two agree almost exactly at 10 reps and diverge from there: Epley returns the higher number on long sets, and Brzycki becomes unstable near 37 reps, where its divisor approaches zero.
Your estimated 1RM is the heaviest load you could lift once, calculated from a set you actually did instead of measured directly. With the Epley formula, 1RM = weight × (1 + reps / 30): 100 kg for 5 reps estimates 117 kg. It is an estimate, not a measurement, and it loses accuracy as reps climb. Under 10 reps it is dependable; past 12 treat it as a reference rather than a number.
What percentage of 1RM does your RIR correspond to?
The formula
Equivalent reps = reps performed + RIR. That total is how many reps you could have done to failure, and it is what you read off the %1RM table. Using Epley inverted: %1RM = 1 / (1 + equivalent reps / 30). A set of 5 with 2 RIR is 7 equivalent reps, so 1 / (1 + 7/30) = 81%.
RIR is the reps you have left in the tank when the set ends. Converting it to a percentage of 1RM needs both numbers: how many reps you did and how many you left. A set of 5 with 2 RIR means you could have done 7, and that lands around 81% of 1RM. The short rule: add reps and RIR together, then read that total off the percentage table. Each extra RIR drops the load by roughly 3 to 4 percentage points.
What plates to load on the bar
The formula
Plates per side = (Total weight − Bar weight) ÷ 2. That figure is then built by always taking the heaviest plate that still fits: 25, 20, 15, 10, 5, 2.5 and 1.25 kg. The smallest jump on the total is 2.5 kg, which is the pair of 1.25s.
Plates per side come from taking the bar off the total and halving what is left: plates per side = (total weight − bar) ÷ 2. With a 20 kg Olympic bar and a 100 kg target, that is 40 kg per side, loaded as one 25 and one 15. With kilo plates the smallest usable jump is 2.5 kg on the total, because the smallest common plate is 1.25 kg and plates always go on in pairs.
How many weekly sets a muscle gets
The formula
Weekly sets = (Sets per session × Sessions per week) + Indirect sets ÷ 2. Halving the indirect work is a counting convention, not a measurement: it expresses that a bench press genuinely loads the triceps but less than a pushdown does, and it avoids the other extreme, which is counting it as zero.
A muscle's weekly volume is the effective sets it receives across the week: weekly sets = (sets per session × sessions per week) + indirect sets ÷ 2. Four chest sets across two sessions plus six pressing sets that also load the triceps give 8 direct and 3 credited, so 11 weekly sets for the triceps. Warm-up sets do not count, and neither do sets left five reps short of failure.
How much relative strength you have
The formula
Relative strength = Total ÷ Body weight, where Total = Squat + Bench press + Deadlift. Wilks and DOTS instead apply a coefficient over body weight, Points = Total × coefficient(weight), with a different polynomial curve per sex: which is why an identical total scores differently across two weight classes.
Relative strength is the total lifted divided by body weight: relative strength = (squat + bench press + deadlift) ÷ body weight. A 360 kg total on an 80 kg body gives 4.5, which is the figure that lets two people of different sizes be compared. Competition coefficients such as Wilks and DOTS solve the same problem with a curve fitted by weight class rather than with a plain division.
What pace you are running
The formula
Pace (min/km) = Time in minutes ÷ Distance in km · Speed (km/h) = Distance ÷ (Time ÷ 60) · Riegel projection: Time₂ = Time₁ × (Distance₂ ÷ Distance₁)^1.06. The 1.06 exponent is the one Peter Riegel fitted on real race results, and it expresses that pace decays slightly as distance grows.
Running pace is time divided by distance: pace = minutes ÷ kilometres. Running 10 km in 55 minutes gives 5.5 min/km, read as 5:30 per kilometre, and equals 10.9 km/h. From one honest performance any other distance can be projected with Riegel's formula, time₂ = time₁ × (distance₂ ÷ distance₁) raised to 1.06: the same 10 km in 55 minutes projects a half marathon of 2 h 1 min.
What your heart rate zones are
The formula
Maximum heart rate (Tanaka) = 208 − 0.7 × age · Heart-rate reserve = Maximum − Resting · Zone bound (Karvonen) = Resting + Reserve × percentage. The five zones use 50-60%, 60-70%, 70-80%, 80-90% and 90-100% of reserve.
Heart-rate zones are calculated on heart-rate reserve, which is maximum minus resting. With the Tanaka formula, maximum heart rate = 208 − 0.7 × age: at 35 that is 184 beats. With a resting rate of 60, reserve is 124, and zone 2 runs from 60 to 70% of that reserve added back to resting — between 134 and 146 beats. Working off maximum alone, without subtracting resting, leaves the low zones too high.
What your VO2 max is
The formula
VO2 max (ml/kg/min) = (Metres in 12 minutes − 504.9) ÷ 44.73 · Absolute VO2 (l/min) = VO2 max × Weight ÷ 1,000 · METs = VO2 max ÷ 3.5 · Speed (km/h) = Metres × 0.005, because 12 minutes is a fifth of an hour.
VO2 max estimated by the Cooper test comes from the distance covered in 12 minutes: VO2 max = (metres − 504.9) ÷ 44.73. Covering 2,400 metres gives 42.4 ml/kg/min, which equals 12.1 METs and a sustained pace of 12 km/h. It is an estimate from a regression fitted on runners, not a laboratory measurement with a gas analyser, and it depends on the test actually being run at maximum effort.
