This PHR calculator converts a whole plastic recipe between 4 units: parts per hundred resin, weight percent, ppm and batch weight in kilograms. The polymer in a phr recipe is always 100 parts, so the total is never 100 and 10 phr is never 10 wt%, which is the error the calculator removes on every row of a formulation.
The calculator opens preloaded with the typical PVC pressure pipe compound published by the Plastics Pipe Institute in TR-2-2023, 8 ingredients totalling 108.03 parts per hundred resin. Every result updates the moment a value changes, the recipe can be exported as a CSV file or an Excel workbook at any point, and the method behind every column is documented below.
PHR calculator
Loaded: PPI TR-2-2023 PVC pressure pipe compound
Recipe in phr
| Ingredient | phr | wt% | ppm |
|---|---|---|---|
| PVC resin | 100.00 | 92.57 | 925,669 |
| Tin heat stabilizer | 0.70 | 0.65 | 6,480 |
| Paraffin wax | 1.20 | 1.11 | 11,108 |
| PE wax | 0.15 | 0.14 | 1,389 |
| Calcium carbonate | 5.00 | 4.63 | 46,283 |
| Titanium dioxide | 0.50 | 0.46 | 4,628 |
| Pigment | 0.03 | 0.03 | 278 |
| Calcium stearate | 0.45 | 0.42 | 4,166 |
| Total | 108.03 | 100.00 | 1,000,000 |
Check passed. Weight percent sums to 100.00.
What the PHR Calculator Converts: Plastic Additive Recipes in 4 Units#
The calculator converts a complete plastic additive recipe, not a single ingredient, in 4 directions: phr to weight percent, weight percent back to phr, phr to a batch weight in kilograms, and weight percent to ppm. A real formulation mixes additive families that are dosed in different units at the same time, and all 43 families of plastic additives are indexed on the root page. A PVC pipe compound, for example, carries its heat stabilizer and lubricants in phr, states its calcium carbonate filler content in wt% on a spec sheet, and reports its clarifier or acid-scavenger level in ppm, so the calculator has to hold all four units for one recipe at once, not convert a single number.
The dosage band an ingredient sits in decides which unit reads naturally. Additives dosed at 150 to 1,200 ppm read as a string of zeros in weight percent, additives dosed at 1 to 10 phr are the PVC and rubber convention, and additives dosed at 10 to 70 percent of the compound, such as plasticizers, fillers and mineral flame retardants, are written in weight percent from the start.
What you enter#
You enter one row per ingredient: a name, a number and the unit the recipe is written in.
- Base polymer and its level, pinned to 100 parts in phr mode
- Each additive, by name and level
- The unit of the column: phr, wt% or ppm
- The additive family, an optional field that flags an unusual level
- Batch weight, needed only in batch mode
- The rounding, from 1 to 4 decimal places
What the calculator returns#
The calculator returns 6 outputs: the total parts, a weight percent column, a ppm column, a phr column, a kilogram column per batch and a validation line that confirms the weight percent column sums to 100.00. The total parts figure is the denominator behind every other column, and in the loaded pipe recipe that total is 108.03 phr, not 100.
| Output | What it is | Formula | Where it is used |
|---|---|---|---|
| Total parts | The sum of every row in the recipe | Σ phr | Denominator of every conversion; 108.03 phr in the loaded example |
| Weight percent | Each ingredient's share of the whole compound | wt%_i = phr_i / Σ phr × 100 | Specification sheets and Tables T2 and T3 below |
| ppm | Weight percent expressed as parts per million | ppm_i = wt%_i × 10,000 | Low-dose additives: clarifiers, acid scavengers, slip agents |
| phr | Parts per hundred resin, reverse mode | phr_i = wt%_i / wt%_polymer × 100 | Converting a supplier's wt% recipe back into phr for a PVC or rubber compound |
| Weight per batch | The mass of each ingredient in a real batch | weight_i = phr_i / Σ phr × batch weight | Scaling a recipe to the plant's mixer size |
| Validation | A check that the weight percent column is internally consistent | Σ wt%_i = 100.00 | Confirms no row was dropped or duplicated before the recipe leaves the page |
How to Convert a Recipe in 6 Steps#
Convert a recipe in 6 steps: enter the base polymer, add the additive rows, name each family, read the total parts, read the weight percent column, then enter a batch weight.
- Enter the base polymer and set it to 100 parts.
- Add one row per additive with its level in phr.
- Name the additive family for each row, so the tool can flag a level that falls outside that family's normal dosage band.
- Read the total parts, which is the denominator of every conversion the calculator performs, not the 100 parts of the base polymer alone.
- Read the weight percent column and check that it sums to 100.00; a green validation banner confirms it, an amber one flags a base polymer that is not fixed at 100 phr.
- Enter a batch weight to convert the same recipe into kilograms for the plant's mixer size.
The 4 Formulas Behind the PHR Calculator#
The calculator uses 4 formulas, one per conversion, and every one of them divides by the total parts of the recipe rather than by the 100 parts of polymer. Each formula below states the same rule the calculator's engine runs, in the order the mode selector lists them.
phr to weight percent#
Weight percent is the ingredient's parts divided by the total parts of the recipe, multiplied by 100. This is the direction most PVC and rubber recipes need first, since the formulation is written in phr and a specification needs weight percent of the compound.
The denominator is the total, not 100: in the loaded pipe recipe the total is 108.03 parts, so 100 parts of PVC are 92.57 wt% of the compound, not 100 wt%.
Weight percent to phr#
To go back to phr, divide the ingredient's weight percent by the base polymer's weight percent and multiply by 100. The reverse direction needs one input the forward direction does not: which row is the base polymer, since every other value is scaled against it.
phr to a batch weight in kg#
A batch weight turns the same recipe into kilograms: divide the ingredient's parts by the total parts and multiply by the batch size. This is the conversion a compounder runs right before charging a mixer, once the recipe and the batch size are both fixed.
At 500 kg, the 5.00 phr of calcium carbonate in the loaded recipe becomes 23.14 kg (calculated from the PPI TR-2 recipe).
Weight percent to ppm#
Weight percent becomes ppm by multiplying by 10,000, so 0.1 wt% is 1,000 ppm. The reverse direction, ppm to weight percent, divides by 10,000 instead.
Clarifiers at 150 to 200 ppm, acid scavengers up to 1,000 ppm and slip agents at 500 to 1,200 ppm are quoted in ppm because the weight percent reads as a string of zeros: 200 ppm is only 0.02 wt%.
Every one of these 4 formulas is implemented exactly as written above; the unit itself, its history and 6 worked conversions are on PHR (parts per hundred resin), which this calculator does not repeat.
Worked Example: a PVC Pressure Pipe Formulation in phr and wt%#
The recipe loaded in the calculator is the Plastics Pipe Institute's typical PVC pressure pipe compound: 8 ingredients, 108.03 total parts, which makes 100 parts of PVC 92.57 wt% of the compound. The recipe is the typical PVC pressure pipe compound published by the Plastics Pipe Institute in TR-2-2023, Appendix C, and it doubles as the calculator's prefilled demo so every plastic formulation can be checked against a sourced starting point before it is changed.
| Ingredient | Additive family | PPI range (phr) | Example (phr) | Weight percent | Per 500 kg batch (kg) |
|---|---|---|---|---|---|
| PVC resin | Base polymer | fixed at 100 | 100.00 | 92.57 | 462.83 |
| Tin heat stabilizer | Heat stabilizer | 0.3-1.0 | 0.70 | 0.65 | 3.24 |
| Paraffin wax | Lubricant | 0.6-1.5 | 1.20 | 1.11 | 5.55 |
| PE wax | Lubricant | 0.0-0.3 | 0.15 | 0.14 | 0.69 |
| Calcium carbonate | Filler | 0.0-5.0 | 5.00 | 4.63 | 23.14 |
| Titanium dioxide | Pigment | 0.5-3.0 | 0.50 | 0.46 | 2.31 |
| Pigment | Colorant | not published in TR-2 | 0.03 | 0.03 | 0.14 |
| Calcium stearate | Lubricant | 0.4-1.5 | 0.45 | 0.42 | 2.08 |
| Total | 108.03 | 100.00 | 500.00 |
phr and the weight percent of PVC, calcium carbonate, paraffin and stabilizer are published in PPI TR-2-2023 Appendix C. The remaining weight percent values and every kilogram value are calculated from the published phr figures with the formulas above.
The smallest row on the sheet shows why the ppm column exists: 0.03 phr of pigment is 0.03 wt% of the compound and 278 ppm (calculated), a level too small to weigh accurately by hand but easy to read as ppm. The full stabilizer package this pipe compound draws on, including how tin, calcium-zinc and lead systems compare, is on additives for PVC.
Which Polymers, Additive Families and Standards Use phr?#
phr is the working unit in PVC, in rubber-modified and peroxide-crosslinked compounds and in highly filled cable compounds, while polyolefins and engineering plastics are dosed in weight percent and ppm. Two US food-contact limits in the same part of the Code of Federal Regulations use different bases: octyltin stabilizers are capped at 3 phr (21 CFR 178.2650) and methyltin stabilizers at 2 wt% of rigid PVC (21 CFR 178.2010), which is exactly the basis confusion this calculator exists to remove.
| Polymer or compound | Additive family | Unit in practice | Sourced example |
|---|---|---|---|
| Rigid PVC pipe | PVC heat stabilizers | phr | tin stabilizer 0.3-1.0 phr (PPI TR-2) |
| Flexible PVC | plasticizers for plastics | phr and wt% | 5-65 wt%, 30-100+ phr |
| PVC and CPVC | impact modifiers | phr | CPE 1-10 phr, 2.5-7.0 preferred |
| HFFR cable | flame retardants for plastics | phr | ATH or MDH 160-180 phr, 61.5 wt% at 160 phr (Huber) |
| Wire and cable compounds | additives for wire and cable compounds | phr | the Huber EVA/LLDPE reference formulation |
| Filled polyolefins | fillers for plastics | wt% | 10-70 % band |
| Polypropylene | antioxidants for plastics | ppm and wt% | acid scavenger up to 1,000 ppm |
| Polyethylene film | slip additives for plastic film | ppm | 500-1,200 ppm |
| Food-contact PVC | (not linked) | phr and wt% in the same regulation | 3 phr organotin, 2 wt% methyltin |
Per-family dosage ranges are collected on Additive Dosage Levels in Plastics (publishing day 7). Carbon black in food contact is capped at 2.5 % by weight of the polymer, not of the compound, under EU 10/2011 FCM 411 and 21 CFR 178.3297.
Export the Result: CSV, Excel and a Shareable Link#
The result leaves the page in 4 ways: a CSV file, an Excel workbook with the formulas live in the cells, a copy button and a shareable link that reopens the recipe.
- CSV file of the result table, for a database or an ERP import
- XLSX workbook with the 4 formulas live in the cells, so the recipe can be edited offline and still recalculate
- Copy-as-table button, for pasting the result straight into a report or an email
- Shareable URL that reopens the exact recipe, with no account needed
Every export above is ungated: three of the four related-search patterns that reach this page ask for a free calculator or a free download, and the map's rule for a tool page is an optional email gate for saving results, never for seeing or exporting them.
Starting Formulation Workbook (XLSX). Sourced starting recipes, preloaded in the calculator's own format, for readers who want more than the one PVC pipe example above. Enter an email, role and company to download it.
5 Checks Before the Number Goes into a Specification#
Check 5 things before a converted number goes into a specification: the basis, the direction, the rounding, the legal basis and whether the plant can weigh the smallest row.
- Basis. Confirm whether a percentage is of the compound or of the polymer; the two are not the same number once fillers are in the recipe.
- Direction. Confirm which row is the base polymer before a reverse conversion, since the wt%-to-phr formula divides by that row specifically.
- Rounding. Keep 2 decimal places for anything under 1 phr, because 0.03 phr rounds to 0.0 wt% at one decimal and the row disappears from the sheet.
- Legal basis. Never compare a migration limit in mg/kg of food with a recipe level; they measure different things entirely.
- Dosability. Confirm the plant can weigh the smallest row on the sheet; ppm-level additives normally arrive as masterbatch, not as a neat powder on a scale.
The 4 bases a converted number can carry are set out below, because a specification that mixes them silently is the most common formulation error this calculator is built to catch.
| Basis | Written as | Example | What it is not |
|---|---|---|---|
| Of the compound | wt% of everything, fillers included | PVC 92.57 wt% in the recipe above | Not a phr value |
| Of the polymer | wt% of the resin only | Carbon black ≤2.5 % w/w of the polymer (EU 10/2011 FCM 411 and 21 CFR 178.3297) | Not 2.5 % of a filled compound |
| Parts per hundred resin | phr | Total organotin ≤3 phr (21 CFR 178.2650) | Not a percentage |
| In the food | SML or OML in mg/kg or mg/dm² | FDA food contact rules and Regulation (EU) No 10/2011 set migration limits, never recipe levels | Not a recipe level at all |
What This PHR Calculator Does Not Do#
The calculator converts units inside one recipe. It does not calculate a masterbatch let-down ratio, plan the compounding step, convert weight into volume or cost, or handle a rubber or epoxy mix ratio. Each boundary below has its own answer elsewhere on the site.
It does not calculate a masterbatch let-down ratio#
A masterbatch dose is the product of two numbers, the let-down percentage and the active content of the concentrate, so it needs its own calculator. Masterbatch active content typically runs 40 to 65 wt%, with extremes from 15 to 80 wt%, and the base polymer takes 1 to 5 percent of it by let-down; the two-number dilution is handled by the let-down ratio calculator, not by this page.
A 35 percent carbon black masterbatch let down at 5 to 6.5 percent, a 19:1 to 14:1 ratio, gives about 1.75 to 2.3 wt% carbon black in a black PE pressure pipe (Ampacet), and typical active contents and masterbatch let-down ratios for other carriers are compared on the masterbatch hub.
It does not plan the compounding step#
A recipe that converts correctly can still be undosable on the line, because ppm-level additives need gravimetric loss-in-weight feeders. Feeding and melting a converted recipe is a separate operation from calculating it, and feeders, side feeding and screw design are covered on plastic compounding.
It does not convert weight to volume or to cost#
Every output on this page is on a mass basis, because a volume or cost conversion needs the density and the price of each ingredient. Cost per kilogram of compound is the sum of each ingredient's weight fraction multiplied by its price, and cost per litre is cost per kilogram multiplied by density, so a filler that lowers cost per kilogram can raise density enough that cost per litre falls by less than expected. Price and density are handled by the additive dosage and cost-in-use calculator, not yet published on this site.
It is not a rubber, epoxy or casting-resin mix-ratio calculator#
The same three letters also stand for parts per hundred rubber, and casting-resin and epoxy suppliers use PHR for a two-component mix ratio. The arithmetic behind a rubber recipe is identical to a plastics recipe, so the calculator works on either, but no rubber, epoxy or coatings dosage appears anywhere on this site, because those industries sit outside its plastics-only scope. A search for "phr calculator" also returns a Finnish business registry, personal health records and an HR certification exam, three unrelated meanings of the same three letters.