Shakeel Muzaffar

How GPA is calculated, explained simply: add up your grade points, then divide by total credit hours. See the grade scale and a full worked example here.

Sleep debt is the gap between the sleep you need and get. You can repay short-term debt with rest, but weekend catch-up cannot fully undo chronic loss.

Sleep runs in roughly 90-minute cycles of light, deep, and REM sleep. Learn how the stages work and how to time the best time to wake up feeling refreshed.

How much sleep you need depends on age: adults need 7 to 9 hours, teens 8 to 10, and kids more. See the full age chart and signs you fall short.

How many steps a day do you need? Benefits rise then plateau near 6,000-8,000 for older adults and 8,000-10,000 for younger. 10,000 is marketing, not science.

Running pace is time divided by distance, and one recent race time can predict your finish at other distances using the Riegel formula. See how it works.

Learn how to find your one-rep max safely by estimating it from a set of 3-5 reps using the Epley and Brzycki formulas, plus a safe true-max protocol.

VO2 max is the ceiling on how much oxygen your body can use during exercise. Learn what it means, what counts as a good score, and how to train to raise it.

Calculate your maximum heart rate fast: subtract your age from 220 for a rough estimate, then use better formulas like Tanaka for a more accurate number.

Heart rate zones are five intensity levels from 50 to 100 percent of your max heart rate. See the 5-zone chart, what each one trains, and how to find yours.