Why Most DIYers Buy 30% Too Much Material
There's a running joke at every hardware store: the guy who comes back twice in one day. Once to return what he over-bought, and once more because he returned too much.
The problem isn't laziness — it's that most people round up "just in case" instead of actually calculating. And that buffer adds up fast.
Here's what over-buying actually costs on common projects:
A 200 sq ft patio at $6/bag for concrete mix. The correct amount is 67 bags. Most people grab 80–90 "to be safe." That's $78–$138 in concrete you'll never use, slowly hardening in your garage until you throw it away next spring.
Mulch is worse. A 500 sq ft garden bed at 3 inches deep needs 4.6 cubic yards. Order 6 "just in case" and you've bought $70 worth of mulch that'll sit in a pile until it decomposes.
Paint? Two gallons of premium interior at $55/gallon that you "might need" for touch-ups. Those cans sit in the basement for 5 years until you're painting a different color anyway.
The fix takes about 2 minutes per material.
Plug your actual dimensions into a calculator. Get the real number. Add the appropriate waste factor (10% for most projects, 15% for diagonal cuts). Done.
HowMuchStuff has 82 free calculators for exactly this — concrete, mulch, paint, roofing, tile, fencing, and a lot more. The waste factors are already built in.
Stop guessing. Stop over-buying. Your garage will thank you.