20 Weeks From Today

Your 20-Week Vertical Tracker

Common 20-Week Starts

One-click jumps for known starts. Each preset sets both the start date and the mode.

Weeks → Calendar-Date Reference Table

Need a different range? Try the 16-week tracker, 12-week tracker, or 52-week tracker.

The Math

Week-by-Week Milestones — Pregnancy

No saved snapshots yet. Tap "Save snapshot" above to keep up to eight 20-week tracks side-by-side.

How to Use the 20-Week Tracker

1. Set the start date — LMP for pregnancy, training plan week-one Monday, or OKR kickoff day. The widget anchors all 20 bars to that date.
2. Pick a mode (pregnancy, training, OKR). The week-by-week milestones below the chart switch to match, citing the ACOG, Pfitzinger, or Wodtke source.
3. Watch the bar fill live. Today's position is marked with a red dot and the current week label appears in the caption beneath the chart.
4. Read the day-140 flag at the top of bar 20 — that is your anatomy scan, race day, or OKR grading day.
5. Add a note and save to localStorage. Up to eight snapshots persist between visits so you can track multiple pregnancies, kids, or training blocks.

Why 20 Weeks Matters

In 2026, the most common reason a person types '20 weeks from today' into a search bar is pregnancy. The 20-week mark is the day of the Level-II anatomy scan, a 30-to-60 minute high-resolution ultrasound that the American College of Obstetricians and Gynecologists (ACOG Practice Bulletin 175, 2016) and the International Society of Ultrasound in Obstetrics and Gynecology (ISUOG, 2010) both recommend for every singleton pregnancy. Twenty weeks is also the midpoint of a 40-week gestation — exactly 140 days from a Last Menstrual Period (LMP) start when counting Naegele's rule weeks.

The second-largest cohort searching this query is endurance athletes. A 20-week training block is the standard plan length for a half-marathon, an Olympic-distance triathlon, or a structured strength cycle. Hal Higdon's 12-week novice plans and Pete Pfitzinger's 18- and 24-week marathon plans bracket the 20-week sweet spot, and the Norwegian Method's threshold-heavy cycles used by Kristian Blummenfelt and Gustav Iden run in 20-week mesocycles. Coaches use the day-140 mark as the deepest point of taper — the moment race-day intensity is locked in.

Twenty weeks is also the standard length of a single OKR cycle when teams extend the traditional 12-week quarter to capture full product launches. Andy Grove invented OKRs at Intel in 1971 and John Doerr brought them to Google in 1999; the modern '20-week' extended cadence appears in Christina Wodtke's Radical Focus (2016) and is used at Stripe, LinkedIn, and many YC-backed startups when a 12-week quarter feels too short for hardware, regulated software, or research projects.

Calendrically, 20 weeks equals exactly 140 days. From a Monday this lands on a Monday; from a Saturday it lands on a Saturday. The math is invariant under daylight-saving transitions because 140 × 86,400 seconds resolves to the same wall-clock weekday regardless of whether one or two DST crossings occur in between. The calendar arithmetic was formalised by the Gregorian reform of 1582 and codified in ISO 8601 (1988) for international interchange.

The neural development packed into 20 weeks of fetal life is staggering. By week 20 the fetus weighs about 320 grams, measures 16.5 cm crown-to-rump, and has formed all four heart chambers, the cerebral cortex, the limb buds, the gonads, and (for female fetuses) all seven million primary oocytes she will ever have. Quickening — the first felt movement — typically arrives between weeks 16 and 18 for multiparous women and 18 to 20 for first-time mothers. The anatomy scan itself measures biparietal diameter, head circumference, abdominal circumference, femur length, and screens for 30+ structural anomalies.

From an athletic-physiology perspective, 20 weeks is roughly the duration of a full block-periodization mesocycle as described by Vladimir Issurin (Block Periodization, 2008). Issurin's model — accumulation, transmutation, realisation — fits a 20-week half-marathon plan as 12 weeks of base, 5 weeks of race-pace, and 3 weeks of taper. Mitochondrial biogenesis driven by zone-2 training has a 12-to-16-week response curve (Holloszy, 1967), which is why elite coaches refuse to compress base phases below 12 weeks.

The tool below renders a vertical 20-bar tracker, fills bars from week 1 upward toward the target date, flags day 140 explicitly, and lets you swap among pregnancy, training, and OKR week-labels. Each preset is sourced from a published reference (ACOG, Pfitzinger, Wodtke) and saved to localStorage so the page survives a refresh.