Cubic feet per second (ft³/s) to Cubic yards per second (yd³/s) conversion

Understanding Cubic feet per second to Cubic yards per second Conversion

Cubic feet per second ($ft^3/s$) and cubic yards per second ($yd^3/s$) are both units of volumetric flow rate, meaning they describe how much volume moves past a point each second. Cubic feet per second is common in hydrology, drainage, and engineering in the United States, while cubic yards per second can be useful when working with larger-scale earthworks, channel flows, or systems where yard-based measurements are preferred.

Converting between these units helps express the same flow in a scale that better matches the application. A value in cubic feet per second may be easier for streamflow records, while cubic yards per second can make very large flows easier to read and compare.

Conversion Formula

Using the verified conversion factor:

$$1\ ft^3/s = 0.03703698259756\ yd^3/s$$

The formula for converting cubic feet per second to cubic yards per second is:

$$yd^3/s = ft^3/s \times 0.03703698259756$$

For the reverse direction, the verified relationship is:

$$1\ yd^3/s = 27.000039686435\ ft^3/s$$

So the reverse formula is:

$$ft^3/s = yd^3/s \times 27.000039686435$$

Step-by-Step Example

Suppose a channel carries $85\ ft^3/s$ of water.

Write the formula:

$$yd^3/s = ft^3/s \times 0.03703698259756$$

Substitute the value:

$$yd^3/s = 85 \times 0.03703698259756$$

Calculate:

$$85\ ft^3/s = 3.1481435207926\ yd^3/s$$

So, a flow rate of $85\ ft^3/s$ is equal to $3.1481435207926\ yd^3/s$.

Real-World Examples

• A small stream measured at $27\ ft^3/s$ corresponds to $1.000\ yd^3/s$ when converted using the verified factor, making it a convenient benchmark flow.
• A stormwater outfall discharging $150\ ft^3/s$ equals $5.555547389634\ yd^3/s$, which may be easier to interpret in large-scale drainage planning.
• A river section carrying $540\ ft^3/s$ converts to $19.9999706026824\ yd^3/s$, useful in flood-control discussions where larger yard-based volumes are preferred.
• A pump or bypass system rated at $12.5\ ft^3/s$ is equivalent to $0.4629622824695\ yd^3/s$, which can help when comparing flow to excavation or material-handling volumes expressed in cubic yards.

Interesting Facts

• Cubic feet per second, often abbreviated as $cfs$, is one of the standard units used in U.S. streamflow reporting and water-resources practice. The U.S. Geological Survey commonly reports river discharge in cubic feet per second. Source: USGS Water Science School
• A cubic yard is equal to 27 cubic feet in customary volume relationships, which explains why cubic yards per second are much larger in scale than cubic feet per second for the same physical flow. Source: Encyclopaedia Britannica - yard

Notes on Using This Conversion

Because cubic yards are larger than cubic feet, the numerical value becomes smaller when converting from $ft^3/s$ to $yd^3/s$. This is normal for unit conversions where the destination unit represents a larger amount of volume.

In practical terms, cubic feet per second is often the more familiar unit for waterways, culverts, pipes, and drainage systems. Cubic yards per second may be more intuitive when comparing water movement with excavation quantities, dredging rates, or large open-channel transport volumes.

For quick reference:

$$ft^3/s \to yd^3/s:\ \times 0.03703698259756$$

$$yd^3/s \to ft^3/s:\ \times 27.000039686435$$

Both units describe the same kind of measurement: volume flowing per unit time. The conversion only changes the scale of the number, not the physical amount of flow.

When documenting engineering calculations, it is useful to keep the unit symbols visible at every step:

$$85\ ft^3/s \times 0.03703698259756 = 3.1481435207926\ yd^3/s$$

This reduces ambiguity and helps confirm that the conversion has been applied in the correct direction.

For tables, reports, and calculators, the same relationship applies consistently:

$$yd^3/s = ft^3/s \times 0.03703698259756$$

This makes the conversion straightforward for anything from small drainage studies to large river or construction flow estimates.

How to Convert Cubic feet per second to Cubic yards per second

To convert Cubic feet per second (ft3/s) to Cubic yards per second (yd3/s), multiply the flow rate by the conversion factor between the two units. Since the factor is known, the process is straightforward.

1. Write the conversion factor:
   Use the verified relationship between the units:

   $$1\ \text{ft}^3/\text{s} = 0.03703698259756\ \text{yd}^3/\text{s}$$

2. Set up the multiplication:
   Multiply the given value, $25\ \text{ft}^3/\text{s}$, by the conversion factor:

   $$25\ \text{ft}^3/\text{s} \times 0.03703698259756\ \text{yd}^3/\text{s per ft}^3/\text{s}$$

3. Calculate the result:

   $$25 \times 0.03703698259756 = 0.9259245649391$$

4. Result:

   $$25\ \text{ft}^3/\text{s} = 0.9259245649391\ \text{yd}^3/\text{s}$$

A quick way to check your work is to confirm the result is smaller than the original number, since a cubic yard is a larger unit than a cubic foot. Keep the full conversion factor for the most accurate result.

What is the formula to convert Cubic feet per second to Cubic yards per second?

Use the verified conversion factor: $1\ \text{ft}^3/\text{s} = 0.03703698259756\ \text{yd}^3/\text{s}$.
To convert, multiply the flow value in cubic feet per second by $0.03703698259756$: $\text{yd}^3/\text{s} = \text{ft}^3/\text{s} \times 0.03703698259756$.

How many Cubic yards per second are in 1 Cubic foot per second?

There are $0.03703698259756\ \text{yd}^3/\text{s}$ in $1\ \text{ft}^3/\text{s}$.
This is the standard factor used to convert from cubic feet per second to cubic yards per second.

Why would I convert Cubic feet per second to Cubic yards per second?

This conversion is useful when comparing flow rates across engineering, construction, and water management projects.
For example, river discharge, drainage systems, or excavation slurry flow may be reported in different volumetric units, and converting to $\text{yd}^3/\text{s}$ can make reports more consistent.

How do I convert a larger flow rate from ft3/s to yd3/s?

Multiply the number of cubic feet per second by $0.03703698259756$.
For instance, if a flow is measured in $\text{ft}^3/\text{s}$, applying $\text{ft}^3/\text{s} \times 0.03703698259756$ gives the equivalent value in $\text{yd}^3/\text{s}$.

Is Cubic yards per second a larger or smaller unit than Cubic feet per second?

Cubic yards per second is a larger volumetric unit than cubic feet per second.
Because of that, the numeric value becomes smaller when converting from $\text{ft}^3/\text{s}$ to $\text{yd}^3/\text{s}$, using $0.03703698259756$ as the multiplier.

Can I use this conversion for water flow and air flow?

Yes, this is a unit conversion for volumetric flow rate, so it applies to any substance measured by volume per time.
Whether the flow is water, air, or another fluid, $1\ \text{ft}^3/\text{s} = 0.03703698259756\ \text{yd}^3/\text{s}$ remains the same.