5:4 · 4 semitones
Major third. Overcharged by about 14 cents.
- Pure
- 386.31¢
- Tempered
- 400¢
- Charge
- +13.69¢
- Beat
- 2.18 Hz
Lower note 220 Hz. Pure upper 275.00 Hz. Tempered upper 277.18 Hz.
This is the claim of the site, and it is willing to be wrong about it: the major third is the interval your ears are most often asked to accept out of tune, and you can hear the cost in ten seconds. Play "both" and count the pulses.
The tempered third sits about 13.7 cents above 5:4. The beats come from nearby harmonics of the two notes failing to meet; a pure 5:4 has none. Major third (Wikipedia, CC BY-SA) gives the tempered third as 13.69 cents wider than 5:4.