Trimming down expenses on project supplies

Had a similar issue with flooring once—grabbed some discounted laminate thinking I'd measured perfectly, but forgot to account for waste from cuts and mistakes. Ended up scrambling to find matching boards online, and of course, the color was slightly off. Now there's a subtle shift halfway down the hallway... barely noticeable, but it bugs me every time I walk by. Curious if anyone's found reliable ways to estimate extra materials without overspending or ending up short?