Formulation Tools
Granulation Moisture & LOD Calculator
Calculate loss on drying, wet-basis and dry-basis moisture, drying target weight, and constant-weight checks for pharmaceutical wet granulation and drying studies.
Quick Answer
Loss on drying (LOD) % = [(wet weight − dry weight) / wet weight] × 100. Dry-basis moisture = mass lost ÷ dry solids × 100. Drying target weight = dry solids ÷ (1 − target wet-basis moisture fraction). LOD measures all volatiles under test conditions — not water alone; compare with Karl Fischer when water-specific limits apply in granulation or API specs.
Final target weight = dry solids / (1 - target moisture fraction)
Granulation moisture calculator
Choose a calculation mode, enter sample or batch weights, then review LOD, drying targets, or constant-weight checks.
Use the same mass unit for both inputs. The result is dimensionless, and mass loss is reported in the same unit entered.
Moisture percentages in this mode are wet-basis values. The dry solids mass is assumed conserved during drying.
Compare two consecutive final weights. For percent tolerance, the difference is calculated relative to the average of the two weights.
Pharmaceutical Granulation Moisture
Moisture content affects granule flow, compaction, tablet hardness, disintegration, coating behavior, and microbial or chemical stability. During wet granulation, development teams often define an inlet temperature, product temperature, airflow, sampling interval, and endpoint moisture range rather than relying on time alone.
LOD is widely used because it is simple and operationally convenient. It should still be tied to a validated method: sample size, drying temperature, drying time or constant-weight rule, pan handling, and acceptance criteria all influence the result.
LOD vs Karl Fischer
Loss on drying
Measures total mass lost under the drying conditions. That loss may include water, residual solvent, or other volatile materials.
Karl Fischer
Measures water more specifically by chemical titration. It is often preferred when water content must be separated from volatile solvent loss.
For hydrates, solvent-containing granules, heat-sensitive actives, or excipients that decompose under drying conditions, LOD and Karl Fischer can move in different directions. Treat method equivalence as a validation question, not a calculator assumption.
Wet Basis vs Dry Basis
| Expression | Formula | Typical use |
|---|---|---|
| Wet-basis moisture | Water mass / total wet mass × 100 | LOD results, batch records, drying endpoints |
| Dry-basis moisture | Water mass / dry solids mass × 100 | Drying science, mass transfer, material balance |
| Residual solids | Dry final mass / initial wet mass × 100 | Quick check of nonvolatile fraction after drying |
Endpoint Setting Notes
A drying endpoint should connect analytical method capability with manufacturability. Too much residual moisture may cause sticking, poor flow, degradation, or microbial risk. Over-drying can create friable granules, weak compacts, static charge, or dissolution shifts.
USP <731> is commonly referenced for loss on drying, but it does not turn a generic temperature and time into a product-specific specification. Use the approved monograph, regulatory filing, validated site method, or development protocol for enforceable limits.
Worked Example
Wet sample weight = 5.000 g. Dry final weight = 4.625 g. Mass loss = 0.375 g.
LOD wet basis = 0.375 / 5.000 × 100 = 7.50%.
Dry-basis moisture = 0.375 / 4.625 × 100 = 8.11%.
Residual solids = 4.625 / 5.000 × 100 = 92.50%.
Initial batch = 125.0 kg at 18.0% moisture. Dry solids = 125.0 × 0.82 = 102.5 kg.
Target moisture = 3.0%. Final target weight = 102.5 / 0.97 = 105.67 kg.
Water to remove = 125.0 - 105.67 = 19.33 kg.
Pharma granulation & CMC context
Wet granulation LOD endpoints feed process validation protocols, fluid-bed or tray dryer set points, and blend uniformity studies. Document wet-basis versus dry-basis moisture in the batch record and align with ICH Q8/Q11 design space when moisture is a critical material attribute for the drug product.
Pair drying calculations with the Compression Force Calculator when endpoint moisture affects tabletability, and with the Yield Calculator for batch reconciliation after drying losses.
Evidence & sources
- PharmaCalculation: Determination of loss on drying
- ICH Quality Guidelines (Q8, Q11)
- USP <731> Loss on Drying — compendial procedure concepts; product monographs define test conditions and limits.
- Competitive landscape: Roboculator LOD calculator computes basic LOD from two weights but lacks wet/dry-basis conversion, drying target mass balance, and constant-weight pass/fail modes for granulation batches. PharmaCalculation LOD articles explain USP procedure text without interactive drying-target or batch-endpoint tools. NovaPharmaNews provides three tabbed modes with formulation hub links — no login required.
Sources and method caveats
- FDA and ICH quality guidance expect scientifically justified, validated analytical procedures for critical quality attributes such as moisture where relevant.
- Karl Fischer references such as ASTM E203 describe water-specific titration; LOD measures gravimetric volatile loss under defined drying conditions.