Running Writings Lab

Ten scientific running calculators in one app: race pace, threshold (LT1 & LT2), critical speed, and adjustments for hills, heat, and wind. The same tools from Running Writings used by tens of thousands of runners, built from the ground up for iPhone and iPad.

PACING & PREDICTION • Race Pace: finish times, splits, and pace conversions for any track, XC, or road distance, including custom distances. • Pace Percentage: calculate paces for Canova-style percentage-based workouts. • Power Law: predict your performances across a wide range of race distances using a power law model.

THRESHOLD & PHYSIOLOGY • Critical Speed: fit a research-grade critical speed model using race or time trial performance. • CV, LT2, and VO₂max Pace: calculate physiologically based workout paces from any race distance 10k and under. • LT1 and Zone 2 Pace: get first lactate threshold and Zone 2 pace from a recent 5k result.

TERRAIN & CONDITIONS • Grade-Adjusted Pace: get GAP adjustments for uphills and downhills. • Heat-Adjusted Pace: adjust long workout paces for heat and humidity. • Wind-Adjusted Pace: see what a headwind costs and a tailwind gives back on point-to-point road runs and races. • Track Wind Adjustments: calculate the net effect of wind around the oval, where every lap has a headwind and a tailwind.

Every calculator is built on published research, with the sources and model details one tap away.

BUILT FOR IPHONE AND IPAD • Pin your favorite calculators to the top of the menu, and long-press the app icon to jump straight to them from your Home Screen. • Set paces and times using haptic dials. • Built-in memory to remember your workout and race paces between sessions. • Set appearance to dark mode, light mode, or auto. • Works completely offline. No account, no sign-in.

THE DEAL One purchase enables every calculator forever. No ads, no subscription, no extra "pro" tier, no tracking, and no analytics. You get the same capabilities as the calculators from Running Writings web tools plus iOS-specific features: offline functionality, haptic dials, input memory, and one-tap access from your Home Screen. Your purchase funds the ongoing research that will power even more scientific running calculators.

WHO IT'S FOR This app is designed for all runners who take their training and racing seriously. Whether you're a marathoner, track athlete, cross country runner, or trail runner, you'll find the tools you need to plan effective workouts and personal-best races.

Built by John J. Davis, Ph.D. - coach, scientist, author of Marathon Excellence for Everyone, and founder of RunningWritings.com.

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