Tools
Reloading calculators
Quick math for the loading bench. Bookmark this page — and if there's a calculator you wish existed, tell us and we'll build it.
Power factor calculator
Power factor = bullet weight (grains) × velocity (fps) ÷ 1,000. Common floors: USPSA Minor 125, Major 165 (Open Major 160). Always confirm against the current rulebook for your sport and division.
Makes USPSA Minor (125+). Below Major floor.
Charge window calculator
Set a target charge and the +/− tolerance you want to allow, and see the acceptance window your powder check needs to hold — and how far outside it a double charge lands.
A double charge (8.40 gr) sits 4.10 gr above your window — any functioning check catches it. The hard part is the partial undercharge just below 4.10 gr: catching that reliably is where measurement resolution matters.
Related reading
How tight can a powder check actually hold that window? See our honest comparison of every powder check system and the squib prevention guide. Our laser powder checks hold windows at micrometer-level resolution and stop a Mark 7 Autodrive automatically.