How much water do I add back to return to the starting solids?

Exactly the pounds evaporated, because the solids never left. In the worked example that is 2,238 lb, about 268 gal if the liquid is water.

How much must I boil off to reach a target solids?

Enter the target as final solids with the density you expect at that strength; liquid evaporated is what the evaporator must remove. Taking 12,500 gal at 9.4 lb/gal from 30 to 45% solids removes about 39,200 lb.

What if final solids come back below starting solids?

Then liquid got in instead of out, and the loss rows turn negative. Live steam injection adds its condensate to the batch; a leaking jacket, coil or rinse valve does the same.

Why not just read the evaporation from the tank level?

Because the level also moves with spills, transfers and temperature, while solids only rise when liquid leaves. Use the level as a check against the volume drop row.

Process Manufacturing calculator

Remaining Liquid After Evaporation Calculator

Find how much liquid a batch lost to evaporation, or must lose to reach a target strength, and the gallons left in the tank. You need the charged volume, both densities and the solids before and after.

What this calculator does

Liquid a batch lost to evaporation, and the batch left, from starting and final solids by mass balance.

Formula used

Starting weight (lb) = starting volume (gal) × starting density (lb/gal)
Solids balance: remaining weight = starting weight × starting solids ÷ final solids
Liquid evaporated = starting weight − remaining weight; evaporation loss (%) = (final solids − starting solids) ÷ final solids × 100
Remaining volume (gal) = remaining weight ÷ final density; volume drop = starting volume − remaining volume

Inputs explained

Starting Batch Volume: Charged volume, from the tank gauge or charge meter.
Starting Batch Density: Weight per gallon at charge, from a density cup or hydrometer.
Starting Solids: Nonvolatile content by weight at charge, from the formula or lab.
Final Solids: Lab result after the step, or the solids you are targeting.
Final Batch Density: Weight per gallon after the step, measured the same way.

How to use the result

Best suited to reconciling a batch that came back over strength, planning boil-down to a target solids, sizing water add-back after a hot hold.
If part of the solids is volatile, it leaves with the vapor and the balance understates the loss. Small solids rises magnify lab error: from 30 to 31.5%, a 0.1-point error in final solids shifts liquid evaporated about 6%.

Current U.S. benchmarks

The producer price index for industrial chemicals stands at 336.006 (BLS, Aug 2026), up 13.3% from a year earlier. Quotes priced off last quarter's material cost miss this move.
The U.S. has 14,543 chemical manufacturing establishments employing about 911,245 workers (Census County Business Patterns, 2023).

Common questions

How much water do I add back to return to the starting solids? Exactly the pounds evaporated, because the solids never left. In the worked example that is 2,238 lb, about 268 gal if the liquid is water.
How much must I boil off to reach a target solids? Enter the target as final solids with the density you expect at that strength; liquid evaporated is what the evaporator must remove. Taking 12,500 gal at 9.4 lb/gal from 30 to 45% solids removes about 39,200 lb.
What if final solids come back below starting solids? Then liquid got in instead of out, and the loss rows turn negative. Live steam injection adds its condensate to the batch; a leaking jacket, coil or rinse valve does the same.
Why not just read the evaporation from the tank level? Because the level also moves with spills, transfers and temperature, while solids only rise when liquid leaves. Use the level as a check against the volume drop row.

Last reviewed 2026-10-01.