Water flow calculator
Convert instant flow, calculate volume over time and compare bottled water costs with a home water filter.
Water flow calculator
Instant flow (L/min)
Instant flow (m3/h)
Water draw time (min)
Volume in selected time (L)
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Volume in selected time (m3)
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Example: if a faucet gives 10 L/min, about 100 liters will pass in 10 minutes.
Cost comparison: bottled water vs home water filter
People in household
1.5 L bottles per person / day
Price per bottle
Deposit per bottle
Bottles / month
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Monthly cost
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Yearly cost
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Potential saving after switching to a filter / month
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Potential saving after switching to a filter / year
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How to read the table
Monthly cost shows the combined spending on bottled water and bottle deposit.
Yearly cost shows the same spending over a full year.
Potential saving after switching to a filter shows money that may stay in your budget, excluding the purchase and service of the filter.
Instant flow is the amount of water delivered per unit of time. For filter, UV or treatment sizing you normally consider peak conditions and acceptable pressure loss.

Flow calculator converts L/min to m3/h and calculates volume over time (e.g., how many liters flow in 10 minutes). It is practical for sizing sediment filters, UV lamps, water treatment systems and for troubleshooting pressure drops and system performance.

For correct sizing, distinguish peak flow from average flow. Equipment is typically selected based on peak demand and acceptable pressure loss.

FAQ - Flow calculator

How do I convert L/min to m3/h?

1 L/min equals 0.06 m3/h. Multiply L/min by 0.06 to get m3/h.

How can I measure flow at home?

Use a bucket of known volume and time how long it takes to fill. Convert the result to L/min.

What is the difference between flow and pressure?

Pressure is the driving force in the system, flow is the amount over time. Low pressure often reduces flow, but they are not the same.

What flow is required for a UV lamp?

It depends on the UV unit and target dose. Too much flow can reduce disinfection because contact time is shorter.

How does flow affect pressure drop across a filter?

Higher flow increases pressure loss. That is why filter selection considers both capacity and allowable pressure drop.

What is peak flow?

Peak flow is the maximum demand when multiple outlets run at once (e.g., shower and faucet). It matters for whole-house sizing.

Why does flow decrease over time?

Common causes are clogged filters, scale/sediment, issues with a pressure reducer, valves or a drop in supply pressure.