Convert temperature and relative humidity to grains per pound (GPP) — the specific humidity restorers track, because RH alone hides how much water the air is actually holding.
What grains per pound tells you
GPP (grains of water vapor per pound of dry air) is specific humidity. Relative humidity moves with temperature, so two rooms at 55% RH can hold very different amounts of water. GPP does not lie — it is the single number to log, compare, and chart across a drying job.
Why restorers use GPP over RH
To dry a structure you have to move water from wet materials into the air and then out through the dehumidifier. That only happens when the air leaving the dehu is lower in GPP than the room. Tracking GPP (and dew point) is how you prove the equipment is actually pulling moisture, not just spinning.
Frequently asked
What is grains per pound?
Grains per pound (GPP) is the weight of water vapor in the air per pound of dry air — 7,000 grains equal one pound of water. It is a direct measure of how much moisture the air holds, independent of temperature.
GPP vs relative humidity — what is the difference?
Relative humidity is a percentage of how much water the air could hold at that temperature, so it changes as the air warms or cools. GPP is an absolute amount that does not change with temperature, which is why restoration techs track it for drying decisions.
What is a normal indoor GPP?
Comfortable indoor air is often around 50–60 GPP. On an active water loss the affected rooms run much higher, and the goal is to drive them down below the dew point of the coldest surface.
More free tools
This knowledge, built into the software
RestoredOS runs the whole job on the same field knowledge behind these tools — drying logs, moisture mapping, scope, and billing.