Millimeter of water to Inch of water Converter (and vice versa)
Created by: tinycalcs.com/en
Number of supported units: 2
Last update: 2026
This converter allows you to convert millimeters of water [mmH₂O, mmWS] to inches of water [inH₂O] or inches of water [inH₂O] to millimeters of water [mmH₂O, mmWS]. Calculations are performed in both directions. The calculation result and the entered value are displayed with up to 20 decimal places for maximum accuracy.
Convert millimeters of water to inches of water
There are two simple ways to convert millimeters of water [mmH₂O, mmWS] to inches of water [inH₂O]. In the first calculation method, the value in millimeters of water [mmH₂O, mmWS] is divided by the rounded conversion factor of 25.3746. The second method multiplies the value in millimeters of water [mmH₂O, mmWS] by the rounded conversion factor of 0.0394.
- Inches of water [inH₂O] ≈ millimeters of water [mmH₂O, mmWS] ÷ 25.3746
- Inches of water [inH₂O] ≈ millimeters of water [mmH₂O, mmWS] * 0.0394
However, rounded conversion values are only suitable for rough conversions, as rounding errors can occur in the calculation result. The most accurate conversion of millimeters of water [mmH₂O, mmWS] to inches of water [inH₂O] can be achieved using the following calculation method.
- Inches of water [inH₂O] = millimeters of water [mmH₂O, mmWS] * 9.80665 ÷ 248.84
Convert inches of water to millimeters of water
Converting inches of water [inH₂O] to millimeters of water [mmH₂O, mmWS] is easy and can be done in two ways. The first method involves multiplication, in which the value in inches of water [inH₂O] is multiplied by the rounded conversion factor of 25.3746. The second variant is a division. Here, the value in inches of water [inH₂O] is divided by the rounded conversion factor of 0.0394.
- Millimeters of water [mmH₂O, mmWS] ≈ inches of water [inH₂O] * 25.3746
- Millimeters of water [mmH₂O, mmWS] ≈ inches of water [inH₂O] ÷ 0.0394
However, rounded conversion values do not allow for exact calculations because rounding errors can occur in the calculation result. The most accurate conversion of inches of water [inH₂O] to millimeters of water [mmH₂O, mmWS] can be achieved using the following calculation method.
- Millimeters of water [mmH₂O, mmWS] = inches of water [inH₂O] ÷ 9.80665 * 248.84
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Millimeters of water
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