By sport
Triathlon Training Zones
Three sports, three anchors: swim CSS pace, bike FTP power, run VDOT pace, each cross-checked with heart rate.
Max Heart Rate Calculator
Your maximum heart rate is the highest your heart can beat at all-out effort. Age formulas estimate it: Tanaka gives 208 − 0.7 × age, the classic 220 − age runs high. At age 35 that is 184 and 185 bpm, but true values vary by ±10–12 bpm, so test it.
Heart Rate Zone Calculator
Heart-rate zones are percentages of your maximum heart rate: Zone 1 is 50–60%, Zone 2 60–70%, Zone 3 70–80%, Zone 4 80–90% and Zone 5 90–100%. At a max of 185 bpm, Zone 2, the aerobic-base zone, is 111–130 bpm. Most easy training belongs in Zones 1–2.
Karvonen Heart Rate Reserve Calculator
The Karvonen formula sets zones from your heart-rate reserve: maximum minus resting heart rate. Target = intensity% × (HRmax − RHR) + RHR. With a max of 185 and resting of 50 bpm (reserve 135), 70% gives 0.70 × 135 + 50 ≈ 145 bpm. The zones follow your fitness.
MAF 180 Formula Calculator
Maffetone's 180 Formula sets your maximum aerobic heart rate at 180 minus your age, adjusted for health and training status. A consistent, injury-free 35-year-old gets 180 − 35 = 145 bpm and an aerobic range of 135–145 bpm. Train at or below it to build the aerobic base.
Friel LTHR Heart Rate Zone Calculator
Joe Friel's heart-rate zones anchor to your lactate-threshold heart rate (LTHR) instead of an age-estimated maximum. Zone 5 splits into 5a, 5b and 5c, so the 5-zone model is usually shown as 7. Threshold (Zone 4) is 94–99% of LTHR for cycling, 95–99% for running. Find LTHR from the last 20 minutes of a 30-minute time trial.
FTP Calculator & Cycling Power Zones
Functional Threshold Power (FTP) is the highest power you can hold for about an hour. The Coggan model sets seven zones from it: Endurance (Z2) is 56–75% FTP and Threshold (Z4) is 91–105%. At an FTP of 250 W, Z2 is 140–188 W, Z4 is 228–263 W, and Sweet Spot is 220–235 W.
Critical Power Calculator (CP & W′)
Critical Power (CP) is the asymptote of the power–duration curve, the highest power you can sustain almost indefinitely. From two maximal efforts, CP = (P1·t1 − P2·t2) ÷ (t1 − t2) and W′ = (P1 − CP)·t1. A 300 W 3-minute and 250 W 10-minute effort give CP ≈ 229 W and W′ ≈ 12.9 kJ.
Running Power Zones Calculator
Running power zones anchor to your running Critical Power (CP), not cycling FTP. The two are not interchangeable. Stryd's five-zone model runs from Easy below 80% CP to Repetition above 115%. At a running CP of 280 W, Threshold tops out at 280 W and Repetition starts above about 322 W.
VDOT Calculator & Running Pace Zones
VDOT is Jack Daniels' single running-fitness number, combining VO₂max and running economy from one race result. A 5 km in 20:00 gives a VDOT of about 49.8. From that one number the model derives every training pace, Easy, Marathon, Threshold, Interval and Repetition, so all your zones come from a single race.
Critical Swim Speed (CSS) Calculator
Critical Swim Speed is your swimming threshold pace, found from two time trials: CSS = 200 ÷ (t400 − t200) in meters per second, and pace per 100 m = 100 ÷ CSS. A 400 m in 6:00 and 200 m in 2:50 give a CSS of about 1.05 m/s, or roughly 1:35 per 100 m, your sustainable threshold pace.
Daily Calorie Calculator
Your daily calorie need is your basal metabolic rate (BMR) multiplied by an activity factor, giving total daily energy expenditure (TDEE). A 35-year-old man, 70 kg and 175 cm, has a BMR near 1,624 kcal. Training at a moderate level (factor 1.55), he needs about 2,517 kcal a day to maintain weight.
Carbohydrate Intake Calculator
Fuel by duration. Under an hour, water is usually enough (0 g/h). From 1 to 2.5 hours, aim for about 60 g of carbohydrate per hour from a single source. Beyond 2.5 hours, you can absorb up to 90 g/h using a glucose-to-fructose mix near 2:1. A 2-hour session needs roughly 120 g total.
Sweat Rate Calculator
Your sweat rate is the fluid you lose per hour of exercise. Weigh yourself before and after a session, add any fluid you drank, and divide by the time. Lose 1 kg in an hour while drinking 500 ml and your sweat rate is 1.5 L/h. On long efforts, replace roughly 100% to 150% of it.
VO2max Estimator
VO2max is the most oxygen your body can use per minute, the ceiling on your aerobic fitness. The 12-minute Cooper test estimates it from distance: VO2max = (meters - 504.9) / 44.73. Run 2,400 meters and you score about 42 ml/kg/min, a recreationally active level. A lab test is more exact, but this gets you close.
BMI Calculator
BMI is your weight in kilograms divided by your height in meters squared. At 70 kg and 175 cm your BMI is 22.9, inside the healthy range of 18.5 to 24.9. It is a fast population screen, but it counts muscle as mass, so lean, muscular athletes often read high.
Running Race Time Predictor
A race time predictor estimates your finishing time at one distance from a result at another using Riegel's formula, T2 = T1 * (D2/D1)^1.06. Enter a recent race, such as 45:00 for 10K, and it predicts roughly 21:35 for 5K, 1:39:17 for a half, and 3:27:01 for a marathon.