You're comparing two industrial pumps. One datasheet lists capacity in pounds per second. The other uses kilograms per hour. Same fluid, same job—completely different numbers on paper. If you guess wrong, you could oversize equipment, blow a budget, or worse, undersize a system that can't keep up.

This guide clears up the confusion. You'll learn what each unit means, how they connect, and how to move between them with confidence.

What Is Mass Flow Rate?

Mass flow rate measures how much material passes through a point in a given amount of time. Think of grain pouring out of a chute or water rushing through a pipe. It answers one question: how many pounds or kilograms move past a fixed spot every second, minute, or hour?

This is different from volumetric flow rate, which tracks volume instead of weight. Mass flow stays constant even when temperature or pressure changes the size of the material. That stability makes it the preferred measurement in engineering, chemistry, and manufacturing.

The Two Units, Defined

Pound Per Second (lb/s)

The pound per second expresses mass flow using the avoirdupois pound—the everyday pound used across the United States. One lb/s means one pound of material crosses your measurement point every single second.

That's a substantial rate. A pound of water is roughly a pint, so 1 lb/s moves about 60 pints per minute. You'll see this unit on high-capacity American equipment: large pumps, industrial conveyors, and bulk material handlers.

Kilogram Per Hour (kg/h)

The kilogram per hour belongs to the metric system, the global standard for science and trade. One kg/h means one kilogram of material flows past your point over the course of an hour.

Notice the built-in difference in pace. The metric unit spreads its count across 3,600 seconds, while the imperial unit counts every second. This mismatch in time scale is why the converted numbers look so much larger—and why mental math trips people up.

How the Conversion Works

Converting lb/s to kg/h involves two simple steps bundled together:

1. Convert the mass: One pound equals exactly 0.45359237 kilograms by international agreement.
2. Convert the time: One hour contains 3,600 seconds, so multiply by 3,600 to stretch the rate across the longer period.

Combine both steps and you get this formula:

kg/h = lb/s × 3,600 × 0.45359237

In practice, most people round the combined result to about 1,632.93. So one pound per second equals roughly 1,633 kilograms per hour. To go the other way, divide your kg/h figure by 1,632.93.

Where You'll Actually Use This Conversion

Cross-Border Equipment Purchases

A plant in Germany buys a feeder built in Texas. The American spec sheet says 12 lb/s. The German control system needs kg/h. Without the conversion, the procurement team can't validate whether the machine meets production targets.

Boiler and Steam Systems

Steam generation is measured by mass, because energy content ties directly to the weight of water converted. U.S. boiler ratings often appear in pounds-based units, while international efficiency reports demand metric figures. Engineers translate between the two constantly.

Food and Chemical Processing

Recipe scaling and batch consistency depend on precise ingredient delivery. A mixer rated in lb/s must match a formulation written in kg/h. Small errors compound across thousands of batches, so getting the math right protects both quality and margin.

Fuel and Combustion Monitoring

Burners, turbines, and engines are tuned around fuel mass. Emissions reporting in most countries requires metric units, while legacy American instrumentation may output imperial ones. Accurate conversion keeps compliance paperwork clean.

Quick Reference Table: lb/s to kg/h

Bookmark these common values. Each figure below applies the full conversion, rounded to two decimal places.

Common Mistakes to Avoid

Confusing Mass Flow With Volumetric Flow

Pounds and kilograms measure weight, not volume. Don't mix these results with gallons-per-minute or liters-per-hour figures. If your source data describes volume, you'll need the material's density first.

Mixing Up lb and lbf

The pound-mass (lb) measures how much matter exists. The pound-force (lbf) measures push or pull. They share a name but describe different things. Flow rate always uses pound-mass.

Rounding Too Early

If you round mid-calculation, small errors grow. Keep full precision through every step, then round only your final answer. For high-volume systems, even a 0.1% drift can mean hundreds of kilograms over a shift.

Forgetting the Time Direction

Going from per-second to per-hour means multiplying by 3,600—not dividing. Going the reverse way means dividing. Double-check which direction you're traveling before you commit to a number.

Your Three-Step Manual Conversion

No calculator handy? Follow this sequence:

1. Write down your lb/s value.
2. Multiply it by 1,632.93 (or the full 3,600 × 0.45359237 for maximum precision).
3. Label the result in kg/h and sanity-check it against the table above.

For the reverse trip, take your kg/h value and divide by 1,632.93. The result lands in lb/s.

The Bottom Line

Pound per second and kilogram per hour measure the same physical reality—mass moving over time—through different unit systems and time scales. Multiply lb/s by roughly 1,632.93 to reach kg/h, and divide to return. Master that one relationship and you can read any spec sheet, from Houston to Hamburg, without hesitation.

Need a specific number right now? Run your value through the converter above and get an instant, precise answer—no mental math required.