Convert SLPM to NLPM or NLPM to SLPM using explicit standard and normal temperature, absolute pressure, and optional gas compressibility factors.

Input flow is in SLPM at the standard reference conditions.

Reference conditions vary by instrument. Both presets use 1 atm (101.325 kPa absolute). Custom pressures must be absolute, and temperatures must exceed −273.15°C.

Gas compressibility

Blank Z values use 1 (ideal gas). Otherwise, use gas-specific values at each reference condition.

Related Calculators

SLPM to NLPM Conversion Formula

The following formula is used to convert the flow rate from slpm to nlpm.

NLPM ≈ SLPM × 0.9318

This approximate factor applies when SLPM uses 20°C and NLPM uses 0°C, with equal absolute reference pressures and ideal-gas compressibility factors (Zs = Zn = 1). Reference definitions vary by instrument or standard.

For general reference conditions, Qn = Qs × (Ps/Pn) × (Tn/Ts) × (Zn/Zs). Here Qs is SLPM, Qn is NLPM, P is absolute pressure in the same units, T is kelvin and Z is the gas compressibility factor at each reference. Reverse conversion uses the reciprocal factor.

Variables:

  • NLPM is the flow rate in normal liters per minute
  • SLPM is the flow rate in standard liters per minute
SLPM to NLPM Conversion Table (SLPM: 20°C, 1 atm; NLPM: 0°C, 1 atm)
SLPM (Standard L/min) NLPM (Normal L/min)
0.50.466
10.932
21.864
32.795
54.659
7.56.988
109.318
1211.181
1513.977
2018.636
2523.294
3027.953
4037.271
5046.589
6055.907
7569.883
10093.178
150139.766
200186.355
300279.533
* Rounded to 3 decimals. Uses K = T_norm/T_std = 273.15/293.15 ≈ 0.9318. Thus, 1 slpm ≈ 0.9318 nlpm.

What are SLPM and NLPM?

SLPM (standard liters per minute) is a unit of flow rate that refers to the volume of gas that passes a point in one minute under standard temperature and pressure conditions. NLPM (normal liters per minute) is another unit of flow rate that refers to the volume of gas that passes a point in one minute under normal temperature and pressure conditions. The conversion between these two units is necessary when comparing flow rates measured under different conditions.

How to Calculate SLPM to NLPM?

The following steps outline how to convert the flow rate from SLPM to NLPM.

  1. First, determine the flow rate in slpm.
  2. Identify both reference temperatures and convert each from degrees Celsius to kelvin by adding 273.15.
  3. Identify both absolute reference pressures in the same units and the corresponding gas compressibility factors; use Z = 1 for the ideal-gas assumption.
  4. Use the formula from above to calculate the flow rate in nlpm.
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem :

Use the following variables as an example problem to test your knowledge.

Flow rate in slpm (SLPM) = 50 slpm

Standard reference temperature (Ts) = 25°C; normal reference temperature (Tn) = 0°C

Both reference pressures = 1 atm absolute; assume Zs = Zn = 1.

NLPM = 50 × (273.15 / 298.15) ≈ 45.8075 NLPM. The 0.9318 factor above is for the different 20°C-to-0°C basis.