Total Alkalinity Calculator

Direction is sign-driven: gap = target − current. A positive gap raises (baking soda); a negative gap lowers (acid); zero is in range. The target is just the number you set — the dose is computed to your target, not snapped to the nearest band edge.

Raise (baking soda):
  lb = (volume_gal × Δppm) / 10,000 × 0.15      # 0.15 = 1.5 lb / 10 ppm
  e.g. (15,000 × 30) / 10,000 × 0.15 = 45 × 0.15 = 6.75 lb

Lower (muriatic acid 31.45%) — shown as a RANGE:
  low  fl oz = (volume_gal × Δppm) / 10,000 × 0.8    # PoolFormula 8 fl oz/10k/10 ppm
  high fl oz = (volume_gal × Δppm) / 10,000 × 2.6    # The Pool Nerd ~26 fl oz/10k/10 ppm
  strength scale = 31.45 / your acid % (applied to both ends)

Why a single point for soda but a range for acid: the baking-soda raise rate is consistent across sources, so it shows as one estimate. The published muriatic-acid rate diverges materially (8 vs ~26 fl oz per 10,000 gal per 10 ppm), so the lower dose is an honest band with the conservative low end as the headline — under-dose and re-test is the safe direction with a corrosive.

Strength matters: the published acid rates assume 31.45% acid. A 14.5% home-store jug needs about ×2.17 as much; we scale both band ends and flag it. Dry acid (sodium bisulfate) has no reliably-published precise TA rate across the sources we cite, so it shows as a labeled approximate band — confirm the rate on the product bag.

Baking soda vs soda ash: baking soda (sodium bicarbonate) raises total alkalinity with little pH change; soda ash (sodium carbonate) raises both pH and TA. This tool doses baking soda only.

Sources: PoolFormula — Pool Alkalinity Calculator (baking-soda raise + 8 fl oz/10k/10 ppm acid low); The Pool Nerd — alkalinity table (1.5 lb/10k/10 ppm raise + ~26 fl oz/10k/10 ppm acid high; ideal bands chlorine 80–120, saltwater 80–100).