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- Weight check helper
There is no calculator on earth that can tell you your correct weight. Body composition, suit age and compression, cylinder material and even how much you have eaten all move the answer. What a calculator can do is give you a published starting point so your first in-water check is close, and then get out of the way. The check itself is what sets your weight.
Where the estimate comes from
| Rule | Value | Source |
|---|---|---|
| Starting lead, 6 mm full wetsuit | 10% of body weight | DAN — Weight Up! |
| Starting lead, 3 mm wetsuit | 5% of body weight | DAN — Weight Up! |
| Fresh water to salt water | add about 1.8 kg (4 lb) | Dive Training |
| Adjustment increment | 0.45–0.91 kg (1–2 lb) at a time | Dive Training |
| Aluminium 80 buoyancy swing | −1.6 lb full to +2.8 lb at 500 psi | DAN — Weight Up! |
| HP steel 80 buoyancy swing | −9 lb full to −3 lb near empty | DAN — Weight Up! |
| Compensation if checking with a full cylinder | add 2–6 lb (0.9–2.7 kg) | Scuba Diving |
The percentage rules assume an average build. A diver with more muscle mass needs proportionally less lead than one with more body fat at the same weight, which is exactly why the number above is a place to start rather than an answer.
The in-water check — this is the part that matters
Do this in shallow water with your buddy present, in the full kit you intend to dive.
- Enter the water with the estimated weight, holding a line or in water you can stand up in.
- Fully deflate the BCD and hold a normal regulator in your mouth.
- Take a normal breath in and hold still. Do not scull, do not fin. You should float at eye level, or between eye level and hairline.
- Exhale fully. You should begin to sink slowly.
- If you float too high, add weight. If you sink on a full breath, remove weight. Change it 0.45–0.91 kg at a time and repeat.
DAN describes the target as floating at eye level with an empty BC and a normal breath, sinking as you exhale DAN — Weight Up!. Dive Training gives the same target as eye level to hairline Dive Training — Pre-Dive Weight Check.
The end-of-dive validation
The real test of your weighting is not at the surface at the start. It is whether you can hold a stop at the end.
If you cannot stay down at that point, you are underweighted. If you need air in the BCD to stay off the bottom for the whole dive, you are carrying too much lead.
Why getting this wrong costs you
- Overweighting forces you to carry a larger gas bubble in the BCD to stay neutral. That bubble adds drag and volume, tips you head-up, raises your air consumption, and increases decompression stress.
- Overweighting also makes ascent control harder, because the bubble you are relying on expands faster as you rise.
- Underweighting makes the last few metres of the ascent a fight, exactly where a controlled ascent rate matters most.
- Underweighting in a drysuit can cause suit squeeze and loss of insulation as you are forced to add gas.
- Do the weight check with a buddy present and in water shallow enough to stand up in or on a line. Never do it alone.
- Re-check your weighting whenever anything changes: a different suit, a different cylinder, fresh versus salt water, a new BCD, or a significant change in your own body weight.
- Never dive underweighted to save effort. Being unable to hold a safety stop is a decompression risk, not an inconvenience.
- Drysuit weighting is a separate skill and should be set with an instructor during drysuit training.