Seal Force Calculator
Work out the total clamping force your sealing bar or tray sealer needs from the seal pressure and total seal area — with switchable units and typical starting parameters by material.
Inputs
Result
Pressure, temperature and dwell values are typical starting ranges for machine set-up — always validate the seal to ASTM F88 and ISO 11607. See the heat seal validation guide.
How to use itCalculate sealing force in three steps
- Select the sealant material. The calculator loads a typical starting pressure, temperature and dwell time for that material — a defensible place to begin, not a finished specification.
- Enter the total seal area — the contact area of the seal (for a tray, the flange area under the sealing tool; for a pouch, the combined seal-band area). Switch between mm², cm² and m² as needed.
- Confirm or adjust the sealing pressure. Change the unit if your machine is specified in bar or psi. The recommended sealing force updates instantly — that is the clamping force your sealing bar, tool or tray sealer must deliver.
Why it mattersWhy seal force is worth calculating
Heat sealing is governed by three parameters — temperature, pressure and dwell time — and pressure is the one most often specified as a machine force. Sealing tools and tray sealers are rated in kN of clamping force, but the parameter that actually makes a seal is pressure (force spread over the seal area). Get the area wrong and a tool that looks powerful enough can under-seal a large flange, or a small seal can be over-compressed to the point of thinning and fibre tear. Converting between pressure and force for your real seal area is the quickest way to check a machine is correctly sized before you commit.
The mathsThe formula
Force comes out in newtons when pressure is in N/mm² and area in mm². The pressure units are interchangeable: 1 N/mm² = 1 MPa = 10 bar = 145.0 psi = 10.20 kg/cm². Worked example: a tray flange of 5,000 mm² sealed at 1 N/mm² needs 5,000 N = 5 kN of clamping force. Double the flange area and you double the force required for the same seal pressure.
ReferenceTypical sealing parameters by material
Starting ranges for common sealant materials. Actual values depend on the specific film, coating, machine and product — treat these as a place to begin, then validate.
| Material | Pressure (N/mm²) | Temperature (°C) | Dwell (s) |
|---|---|---|---|
| PET / APET (tray + lidding) | 0.5–2.0 | 160–200 | 0.5–2.0 |
| CPET tray + peelable lid | 0.5–1.5 | 150–190 | 0.8–2.0 |
| PE / LDPE film | 0.3–0.7 | 120–160 | 0.5–1.5 |
| PP / CPP film | 0.3–0.7 | 140–180 | 0.5–1.5 |
| PETG | 0.4–1.0 | 130–170 | 0.5–1.5 |
| PVC | 0.3–0.7 | 130–170 | 0.4–1.0 |
| Tyvek (heat-seal coated) | 0.2–0.5 | 110–140 | 0.5–1.5 |
| Coated paper / board | 0.3–0.8 | 130–170 | 0.5–1.5 |
Next stepHow to validate the seal
A calculated force is a starting point, not proof of a good seal. Establish the real sealing window on your machine and material, then qualify it: measure seal strength to ASTM F88, check integrity with dye penetration (ASTM F1929) or burst testing, and for sterile medical packaging validate the process (IQ/OQ/PQ) under ISO 11607. Our heat seal validation guide walks through the full path.
FAQFrequently asked questions
How do I calculate sealing force?
Multiply the sealing pressure by the total seal area: Force = Pressure × Area. With pressure in N/mm² and area in mm², the force is in newtons. For example, 1 N/mm² over a 5,000 mm² flange needs 5,000 N (5 kN) of clamping force.
What sealing pressure should I use?
It depends on the material and format. Typical starting ranges are roughly 0.2–0.5 N/mm² for coated Tyvek, 0.3–0.7 N/mm² for PE and PP films, and 0.5–2 N/mm² for PET tray-and-lid sealing. Always validate the final pressure on your machine and material.
What units is sealing pressure measured in?
Sealing pressure is a pressure, so any pressure unit works: N/mm² (identical to MPa) is common in tooling, while machines are often specified in bar or psi. 1 N/mm² = 1 MPa = 10 bar = 145 psi = 10.2 kg/cm². This calculator converts between them.
Does higher pressure make a better seal?
Not necessarily. Pressure must be high enough to bring the sealing surfaces into intimate contact, but too much can thin the material, cause fibre tear on porous webs like Tyvek, or create a seal that will not peel cleanly. The right pressure is validated, not maximised.
How do I convert N/mm² to bar or psi?
Multiply N/mm² by 10 to get bar, or by about 145 to get psi. So 1.5 N/mm² is 15 bar or roughly 218 psi. The unit selector on the calculator does this automatically.