Tools you might need next
Calculate scuba air usage rate at depth from SAC rate and dive depth. Estimate PSI per minute, cu ft consumed, and remaining dive time from tank pressure.
Calculate surface air consumption (SAC) rate for scuba divers. Enter tank PSI used, dive time, and depth to estimate cu ft/min at the surface.
Plan safe recreational scuba dive profiles from air supply, depth, and SAC rate. Estimate bottom time, turn pressure, and remaining gas at ascent.
Recreational rule-of-thumb starts at 2.5–3.5% of body weight in fresh water, 4–6% in salt water. This varies significantly by body composition and lung volume.
Base weight (lb) ≈ Body weight (lb) × 0.025–0.035 (fresh) or × 0.04–0.06 (salt)Neoprene compresses at depth, but at the surface a thick wetsuit or dry suit with undergarments adds substantial positive buoyancy requiring compensating weight.
Add 4–6 lb (3mm), 6–10 lb (5mm), 10–16 lb (7mm/dry)Aluminum tanks shift from negative to positive buoyancy as they empty. Steel tanks remain negative throughout the dive. Add weight for camera housings, lights, and other positively buoyant gear.
AL80: +2–4 lb start, −2 to +1 lb end | Steel: −2 to −6 lbUpdated: July 2026
A 180 lb diver in a 3mm shorty with AL80 might start with 12–14 lb, then fine-tune to 10–12 lb after a buoyancy check with 500 PSI remaining.
A 160 lb diver in a dry suit with heavy undergarments in salt water may need 22–28 lb total, distributed between weight belt and integrated pockets for trim.
Moving from AL80 to LP85 steel may require removing 4–6 lb of lead since steel tanks remain negatively buoyant when empty. Recalculate before the first dive on new tanks.
Proper weighting is essential for safe, efficient diving — too much lead wastes air fighting buoyancy; too little makes safety stops difficult. Enter body weight, exposure protection, tank type, and water type to estimate starting ballast weight before a proper in-water buoyancy check.