Tiles are 10 degrees by 10 degrees at the equator.
The tile coordinate system starts at (0,0) (horizontal tile number, vertical tile number) in the upper left corner and proceeds right (horizontal) and downward (vertical). The tile in the bottom right corner is (35,17).

Use the MODIS Tile Calculator to
- determine the MODIS tile, and line, pixel within the tile for any lat/lon point
- determine the lat/long for a MODIS line, pixel within a tile