A Dive Log That Does the SAC Math, Without an Account

Every online dive log worth using — divelogs.org, LogMyDive, PADI’s app — asks you to create an account before you can save a single dive. Subsurface skips the account but asks you to install desktop software instead. None of them are wrong to do this; syncing across devices genuinely needs an account somewhere. But if you just want to log a dive and see your air consumption trend, that’s a lot of setup for a small task.

The free Dive Log & Gas Tracker skips all of it — open the page, log the dive, done.

Where the gap actually is

Online dive logs (divelogs.org, LogMyDive, PADI) all require an account, which makes sense if you’re syncing a dive computer across a career of diving — overkill if you’re logging from a phone browser between dives on a boat.

SAC/RMV calculators (there are at least half a dozen: DiveCalc, Scuba Test Online, JCA Elite Scuba, and others) do the math for exactly one dive at a time. Close the tab, and the number is gone — there’s no history, no trend, nothing to compare your next dive against.

Printable dive log pages (ScubaBoard threads, Etsy, SeaCrush) are free and require nothing, but they’re static — you’re doing the SAC arithmetic by hand, if you do it at all.

What’s missing is the middle: something that saves your dives and calculates SAC/RMV for each one automatically, without asking for an account.

What it does

Logs a dive — site, date, avg/max depth, bottom time, cylinder size, start and end pressure, in metric or imperial.
Calculates SAC and RMV automatically for every entry, using the same formulas printed in most dive training manuals: ATA from average depth, SAC from pressure used over time and ATA, RMV from SAC times cylinder volume.
Tracks a SAC trend across your logged dives, so you can actually see whether your air consumption is improving — the clearest single sign that your buoyancy and breathing are getting more efficient.
A gas planner for MOD, EAD and PO₂ at depth — useful for nitrox divers checking a mix against a planned depth without pulling out a table.
Exports to CSV or a JSON backup, and prints a clean dive-log table for anyone who still wants a paper record too.

What it doesn’t do

It’s not a dive computer, doesn’t download from one, and doesn’t replace decompression planning software or your agency’s tables. It doesn’t sync across devices on its own — export a backup and import it elsewhere if you switch devices. And everything lives in this one browser; clear your browsing data without exporting first, and the log goes with it.

FAQ

What counts as a good SAC rate? Recreational divers typically fall in a 15–20 L/min range; experienced divers with strong buoyancy control often see SAC rates under 15 L/min, while newer divers are commonly above 25 L/min, per Blue Grotto Dive Resort’s explainer on SAC and RMV. Your own trend matters more than any single number — cold water, stress and current all push it up temporarily.

Does the site rotation or depth math replace training? No — the gas planner is a quick-reference calculator for divers already trained in nitrox use, not an instruction manual.

Can I log dives on air and nitrox in the same tracker? Yes, there’s no separate mode — just log the cylinder and gas details per dive.

Is there a paper version that matches this? Yes — Dive Log Book covers the same fields plus certification records, equipment log and a full gas quick-reference, for the boat trips where you’d rather not bring a laptop.

Try the free Dive Log & Gas Tracker — no account, nothing to install.