How It Works
The calculator reads each birthdate in three ways and then blends the results. No names, birth times or locations are needed.
Life Path numbers (45% of the score)
Each full birthdate is reduced to a Life Path number, the core number in numerology. The pair is then looked up in a chart that rates every combination between 35% and 95%.
Biorhythm sync (35%)
Biorhythm theory describes three cycles that start at birth: physical (23 days), emotional (28 days) and intellectual (33 days). The tool checks where both people sit on each cycle on your chosen date and scores how closely they match.
Birthday numbers (20%)
The day of the month you were born is reduced to one digit. Identical birthday numbers score 100%, numbers within two of each other score 75%, and anything further apart scores 50%.
If either person has a master number (11, 22 or 33), a 5 point bonus is added. The final score is capped at 99%.
What Is the Formula?
- LP: the Life Path pair score from the chart; master numbers are treated as 9 for this lookup.
- Bio: the average of the three cycle sync scores.
- BD: the birthday number match: 100, 75 or 50.
- M: the master number bonus: 5 if either Life Path is 11, 22 or 33, otherwise 0.
Sync for a single biorhythm cycle
- t: days since each person's birth on the chosen date.
- C: the cycle length: 23, 28 or 33 days.
- Position: runs from negative 1 (low) to positive 1 (peak), so identical positions give 100% and opposite extremes give 0%.
Life Path Compatibility Chart
Here is how the calculator rates each Life Path number against its strongest and most challenging matches.
| Life Path | Best matches | Most challenging |
|---|---|---|
| 1 | 5 (90%), 3 (85%) | 4 (50%) |
| 2 | 6 (95%), 4 (85%) | 5 (45%) |
| 3 | 9 (95%), 6 (90%) | 4 (40%) |
| 4 | 8 (90%), 2 and 7 (85%) | 5 (35%) |
| 5 | 1 (90%), 3 and 9 (85%) | 4 (35%) |
| 6 | 2 (95%), 3 and 9 (90%) | 5 (45%) |
| 7 | 4 (85%), 5 (80%) | 8 (40%) |
| 8 | 4 (90%), 1 (80%) | 7 (40%) |
| 9 | 3 (95%), 6 (90%) | 4 and 8 (55%) |
Worked Example
Person A was born on 12 March 1990 and Person B on 25 July 1993. The biorhythm date is 1 January 2026.
- Life Path A: 1+9+9+0+0+3+1+2 = 25, then 2+5 = 7.
- Life Path B: 1+9+9+3+0+7+2+5 = 36, then 3+6 = 9. The 7 and 9 pairing scores 70% on the chart.
- Birthday numbers: 12 becomes 1+2 = 3, and 25 becomes 2+5 = 7. They differ by 4, so this part scores 50%.
- Biorhythm on 1 January 2026: physical 23%, emotional 92%, intellectual 66%, for an average of 60%.
- Total: 0.45 × 70 + 0.35 × 60 + 0.20 × 50 = 31.5 + 21 + 10 = 62.5, which rounds to 63%.
A score of 63% falls in the Intriguing Potential tier. Check the same pair a week later and only the biorhythm share will move.