Scuba Weight Chart by Body Weight and Suit
A scuba diver in a 5 mm full wetsuit starts with 8 to 10 percent of body weight in lead, so a 180 lb diver starts at 14 to 18 lb. A 3 mm full is 5 to 7 percent and a 7 mm with a hood is about 10 percent. Salt water needs roughly 2.5 percent more than fresh, and the weight check is done at the END of a dive because an aluminium 80 goes about 4 lb positive at 500 psi.
Correct weighting is the amount of lead that lets you hold a safety stop at 15 feet, with an empty BCD and a near empty cylinder, without finning to stay down. Everything else is a way of getting to that test. The chart below gives a starting figure by body weight and exposure suit, and the rest of the page is about the correction that follows, because a starting figure that is never corrected is just a guess with a table behind it.
Two facts drive every number here. Neoprene floats, so more suit means more lead. And a cylinder gets lighter as you breathe it, so the lead that felt right at the start of the dive is not the lead that matters at the end of it. Hold on to both and the rest of the chart follows.
How much lead do you start with?
Find your body weight in the first column and read across to your exposure suit. These are starting points for salt water diving with an aluminium cylinder, which is the most common combination, and every one of them is a place to begin rather than a number to trust.
| Body weight | Metric | Skin or swimsuit | 3 mm shorty | 3 mm full | 5 mm full | 7 mm plus hood | Drysuit |
|---|---|---|---|---|---|---|---|
| 120 lb | 54 kg | 0 to 2 lb | 6 lb | 6 to 8 lb | 10 to 12 lb | 12 lb | 16 to 20 lb |
| 140 lb | 64 kg | 0 to 2 lb | 7 lb | 7 to 10 lb | 11 to 14 lb | 14 lb | 18 to 22 lb |
| 160 lb | 73 kg | 0 to 2 lb | 8 lb | 8 to 11 lb | 13 to 16 lb | 16 lb | 20 to 24 lb |
| 180 lb | 82 kg | 0 to 2 lb | 9 lb | 9 to 13 lb | 14 to 18 lb | 18 lb | 22 to 26 lb |
| 200 lb | 91 kg | 0 to 2 lb | 10 lb | 10 to 14 lb | 16 to 20 lb | 20 lb | 24 to 28 lb |
| 220 lb | 100 kg | 0 to 2 lb | 11 lb | 11 to 15 lb | 18 to 22 lb | 22 lb | 26 to 30 lb |
| 240 lb | 109 kg | 0 to 2 lb | 12 lb | 12 to 17 lb | 19 to 24 lb | 24 lb | 28 to 32 lb |
| 260 lb | 118 kg | 0 to 2 lb | 13 lb | 13 to 18 lb | 21 to 26 lb | 26 lb | 30 to 34 lb |
| 280 lb | 127 kg | 0 to 2 lb | 14 lb | 14 to 20 lb | 22 to 28 lb | 28 lb | 32 to 36 lb |
The percentages behind the grid are 5 percent for a 3 mm shorty, 5 to 7 percent for a 3 mm full, 8 to 10 percent for a 5 mm full, about 10 percent for a 7 mm full with a hood, and 10 percent plus a further 4 to 8 lb for a drysuit with an undergarment. A skin or swimsuit needs almost nothing, typically 0 to 2 lb, which is why that column is a flat figure rather than a percentage.
Read one row to see how much the suit matters. A 180 lb diver needs 9 to 13 lb in a 3 mm full and 14 to 18 lb in a 5 mm. That step, which is nothing more than 2 mm of neoprene, is the single largest jump on the ladder, and it is the reason a diver who changes suits and keeps the same belt has a difficult dive. The wetsuit thickness chart shows which suit the water actually calls for.
The drysuit column carries a caveat the others do not. A drysuit's buoyancy depends almost entirely on the undergarment inside it and on how much air you are carrying in the suit, so the spread on that column is wider in practice than the table can show. Drysuit diving needs its own certification precisely because you are now managing two air spaces instead of one, and a trilaminate drysuit should be bought after that course rather than before it.
Why is the weight check done at the end of the dive?
Because an aluminium 80 goes about 4 lb positive at 500 psi. The gas inside a full one weighs roughly 6.2 lb, and you breathe that weight away over the dive. A diver weighted to be neutral on the boat with a full cylinder is therefore around 4 lb light at the safety stop, which is the exact moment when being light is most dangerous, because the last 15 feet is where pressure changes fastest and where an uncontrolled ascent does the most harm.
So the check tests the worst case. At the end of a dive, in water too deep to stand in, with about 500 psi remaining, dump every bubble out of the BCD. Hold a normal breath and float upright, relaxed, without finning. Correct weighting puts the water at eye level, and you should sink slowly as you exhale. If you sink while holding the breath, you are heavy. If your shoulders stay clear of the surface, you are light. Adjust in 2 lb steps, which is why weights that come in small increments are more useful than a few large blocks.
Steel cylinders change the arithmetic rather than the method. Steel stays negatively buoyant throughout the dive, so the swing never crosses zero and a steel diver carries roughly 4 to 6 lb less on the belt for the same suit. That is genuinely less lead to hump down a jetty, and it is one of the main practical arguments in the aluminium versus steel comparison. The figures for every common cylinder are on the tank specifications chart.
How much more lead does salt water need?
Salt water is denser than fresh, so everything immersed in it floats more, and the correction runs to roughly 2.5 percent of your total immersed weight. Note that this is total immersed weight, meaning you plus your gear, rather than body weight alone. The table below assumes about 40 lb of gear in the water, which is a reasonable single cylinder recreational figure, and shows the difference for a 5 mm full suit at 9 percent.
| Body weight | Plus gear | Salt water, 5 mm | Fresh water, 5 mm | Difference |
|---|---|---|---|---|
| 120 lb | 160 lb | 11 lb | 7 lb | 4.0 lb |
| 140 lb | 180 lb | 13 lb | 9 lb | 4.5 lb |
| 160 lb | 200 lb | 14 lb | 9 lb | 5.0 lb |
| 180 lb | 220 lb | 16 lb | 11 lb | 5.5 lb |
| 200 lb | 240 lb | 18 lb | 12 lb | 6.0 lb |
| 220 lb | 260 lb | 20 lb | 14 lb | 6.5 lb |
| 240 lb | 280 lb | 22 lb | 15 lb | 7.0 lb |
| 260 lb | 300 lb | 23 lb | 16 lb | 7.5 lb |
| 280 lb | 320 lb | 25 lb | 17 lb | 8.0 lb |
The practical consequence bites hardest on the first dive of a trip. A diver who trained in a freshwater quarry and has dialled in a belt over twenty local dives will be underweighted on their first ocean dive, and will discover it at the safety stop rather than on the descent. The same applies in reverse: divers arriving at altitude lakes from the coast are routinely overweighted. Plan on a proper weight check on the first dive whenever the water changes.
What else moves the number?
Weighting is not a fixed personal constant. It is a property of a specific combination of diver, suit, cylinder and water, and changing any one of them changes the answer.
| Change | Direction | Approximate size | Note |
|---|---|---|---|
| Salt water instead of fresh | Add | About 2.5% of total immersed weight | A quarry weighting is not a boat weighting |
| Aluminium cylinder instead of steel | Add | 4 to 6 lb | Steel stays negative all dive, aluminium does not |
| Adding a hood | Add | 1 to 3 lb | Neoprene at the head is still neoprene |
| Adding gloves and boots | Add | 1 to 2 lb | Small individually, real when combined with a hood |
| A new suit rather than a compressed old one | Add | 2 to 4 lb | Neoprene loses buoyancy as it ages and compresses |
| Moving from a 3 mm to a 5 mm suit | Add | About 3% of body weight | The largest single step on the ladder |
| A camera rig or a heavy light | Subtract | Its own negative buoyancy | Weigh the rig in the water before guessing |
| Better breathing control and trim | Subtract | 2 to 6 lb over a season | Most new divers are overweighted, not underweighted |
The last row is the one worth taking seriously. Most divers are overweighted for their first fifty dives and get lighter as their breathing settles and their trim improves. Rechecking your weighting once a season, rather than treating the number you were handed on your course as permanent, tends to give back 2 to 6 lb. Adding a neoprene hood or moving from a 3 mm to a 5 mm suit pushes it the other way, and both are worth a fresh check rather than an estimate.
Why is being overweighted worse than it feels?
Because the lead does not stay a lead problem. Carrying 6 lb more than you need means carrying 6 lb of compensating air in the BCD, which makes you a bigger and softer shape in the water, adds drag, and tips you into a head up, feet down posture that turns every fin kick into a downward push at the reef. Gas consumption rises accordingly, which is why overweighted divers are usually the first ones back on the boat.
The safety argument is sharper. Air in a BCD expands on ascent, and the more you are carrying, the more aggressively it expands and the faster it needs venting. The diver most likely to have a runaway ascent is not the light one. It is the heavy one who was managing a large bubble and lost control of it at 20 feet. Being a little heavy feels reassuring on the descent, which is exactly why the habit persists.
There is a floor, though, and it is worth stating so the advice does not read as one directional. You need enough lead to hold a safety stop at the end of the dive with an empty BCD and a near empty cylinder, and enough to make a controlled descent without fighting. Underweighted divers fin downwards to descend, arrive at the bottom out of breath, and cannot hold a stop at all. The target is the eye level float, not the lightest belt in the group.
Where should the weight sit?
Total weight sets buoyancy; placement sets trim, and they are separate problems that a single belt tends to conflate. Piling everything on the hips pulls the lower body down and forces a head up posture that no amount of finning fixes. Splitting the same total between integrated BCD pockets, trim pockets on the tank bands and a belt lets you lie flat, which is worth more to your gas consumption than any change to the total.
Soft weight bags sit against the hip and conform rather than digging in, and because they come in small increments they let you make the 2 lb adjustments a weight check actually calls for. If your BCD has no integrated system, a pocketed weight belt is the straightforward answer, and a cheaper four pocket belt does the same job on a budget. Whatever you use, the release must be operable with one gloved hand without looking. The BCD roundup covers integrated weight systems and how positively they lock.
Run your own numbers rather than reading a grid row: the weighting and buoyancy calculator takes your body weight, suit, cylinder and water type, and the buoyancy and weighting guide covers the in-water technique that turns a correct weight into good buoyancy control.
Related charts and tools
- Weighting and buoyancy calculator, for your exact setup
- Wetsuit thickness chart, because the suit sets the lead
- Tank specifications chart, and the buoyancy swing per cylinder
- Buoyancy and weighting guide, the technique half
- Aluminium versus steel cylinders, and what each does to your belt
Frequently asked questions
How much weight do I need for scuba diving?
As a starting point, about 5 to 7 percent of your body weight in a 3 mm full wetsuit, 8 to 10 percent in a 5 mm, and about 10 percent in a 7 mm with a hood. A 180 lb diver in a 5 mm therefore starts with 14 to 18 lb. Those are starting points only. The real figure comes from a weight check done at the end of a dive with a near empty cylinder.
Why is the weight check done at the end of a dive?
Because an aluminium 80 goes about 4 lb positive as it empties. A diver weighted to be neutral with a full cylinder will be roughly 4 lb light at the safety stop, which is exactly where being light turns a controlled ascent into an uncontrolled one. Checking on a near empty cylinder tests the worst case rather than the best case, and that is the only case worth testing.
How do you do a proper weight check?
At the end of a dive, in water too deep to stand in, with about 500 psi left, empty your BCD completely. Hold a normal breath and float upright. You are correctly weighted when the water sits at eye level and you sink slowly as you exhale. If you sink while holding the breath you are heavy. If your shoulders stay clear of the water you are light.
Do I need more weight in salt water than fresh?
Yes. Salt water is denser, so everything in it floats more, and the difference runs to roughly 2.5 percent of your total immersed weight. For a 180 lb diver carrying about 40 lb of gear that is roughly 5.5 lb of lead between a quarry and the ocean. Divers who train inland and then dive salt water for the first time are routinely underweighted on the first dive of a trip.
What happens if I am overweighted?
You compensate by carrying more air in the BCD, which makes you a larger and less stable shape, increases drag, forces a head up swimming posture and wastes gas. Worse, that extra air expands on ascent, so an overweighted diver is also the diver most likely to have a runaway ascent. Being a few pounds heavy feels safe and is one of the more common causes of poor buoyancy control.
Where should the weight actually sit?
Split it rather than stacking it all on a belt at the waist. Integrated BCD pockets, trim pockets on the tank bands and a belt each pull your body into a different attitude, and moving 2 lb from the hips to the upper back is often the difference between fighting to stay horizontal and simply lying flat. Total weight fixes buoyancy. Weight placement fixes trim.
How we choose: we compare published manufacturer specifications, published training agency standards, and verified owner reviews across retailers. We do not test gear in person, and every depth rating, cylinder capacity and algorithm name quoted here is the manufacturer's published figure unless we say otherwise, so confirm it on the current spec sheet before you buy. Nothing here is dive instruction, and no calculator output on this site is a dive plan. Scuba diving carries a real risk of decompression sickness, oxygen toxicity, barotrauma and drowning. Dive within the limits of your certification, verify every plan with your own computer, and buy the training before the gear that assumes it.
Logging your own SAC rate and gas plans? The Dive Kit & Air Planning Workbook is the paid version of these pages: 8 printable worksheets you fill in with your own numbers, plus the full PDF, $29.