Ironically, a band that is can feel tighter than it actually is. When the band doesn't provide 80% of the support, the breasts pull the cups forward and down, tilting the band up your back and causing it to "saw" into your skin. Always ensure the band is level across your back for the most comfortable distribution of weight.
If the band is too tight, the straps often work overtime, digging painful channels into your shoulders. tight bras busty
You should be able to slide two fingers comfortably under the band at the back. If you can’t, the band is too small. Ironically, a band that is can feel tighter
If the cup fits but the band is tight, go up one band size and down one cup size (e.g., if a 34G is tight, try a 36F). If the band is too tight, the straps
These are inexpensive tools that add an inch or two to your current bras without compromising the cup shape.