Estimate flow for experiments, HVAC, or piping scenarios. Choose a method, set units, view derived velocity, and download reports. Built for fast, reliable checks.
| # | Scenario | Method | Inputs | Computed flow | Notes |
|---|---|---|---|---|---|
| 1 | Bucket test | V / t | 2.5 L over 15 s | 10.000 L/min | Good for quick verification. |
| 2 | Vent duct | A · v | 0.20 m² and 3.0 m/s | 0.600 m³/s | Matches a steady flow estimate. |
| 3 | Water line | ṁ / ρ | 0.25 kg/s and 998 kg/m³ | 0.0150 m³/s | Use temperature-correct density. |
| 4 | Pipe velocity check | A · v + diameter | 25 mm diameter and 1.8 m/s | ~5.30 L/min | Also outputs derived velocity. |
Volumetric flow, Q, links motion to capacity in fluids and gases. In teaching labs it validates pump curves, nozzle coefficients, and calibrated rotameters. In ventilation studies it anchors air‑change calculations and occupant load assumptions. Even a 10 L/min deviation can shift Reynolds number enough to change regime classification, friction factors, and uncertainty budgets.
The calculator implements V/t for bucket timing, A·v for duct and pipe sections, and ṁ/ρ when mass flow is instrumented. Each method reflects a different sensor pathway: stopwatch and container, velocity probe and geometry, or mass scale and density table. Conversions standardize inputs to SI before solving, reducing unit‑mix mistakes that often inflate results by factors of 60, 3.6, or 1000.
Results can be displayed as m³/s, L/s, L/min, m³/h, CFM, and GPM to match typical specifications. For example, fans are frequently rated in CFM, while lab reports prefer m³/s. Exporting CSV preserves timestamped runs for averaging, standard deviation, and traceable documentation. The PDF summary is useful for quick sign‑off during commissioning or practical exams.
When diameter is supplied, area is computed as π(d/2)² and the tool can estimate average velocity from Q/A. This is a bulk estimate; real profiles are nonuniform and depend on entrance length. In turbulent flow, centerline speed can exceed the average by roughly 10–30%, while laminar flow shows a factor of two. Use the derived velocity as a check, not a replacement for a profile measurement.
Repeat at least three trials and compare the spread against your required tolerance. If V/t and A·v disagree, inspect timing reaction, leakage, bubbles, and probe alignment. For liquids, update density for temperature; water changes by about 0.3% between 20°C and 30°C, and oils vary more. For gases, density depends on pressure and temperature, so a single constant may understate flow in wide operating ranges. Record instrument models and calibration dates to keep your results defensible today.
Use V/t for timed collection, A·v for known area with average velocity, and ṁ/ρ when mass flow and density are available. Pick the path that matches your instruments and least assumptions.
Most spikes come from unit mistakes: minutes typed as seconds, liters typed as cubic meters, or mph interpreted as m/s. Recheck each unit selector and confirm the base m³/s value seems reasonable.
Yes, for the Area × Velocity method it computes area from diameter using π(d/2)². Your manual area field is ignored while the diameter option is enabled.
Use temperature‑appropriate density when possible. Around room temperature, water is close to 998–1000 kg/m³, but warmer water is slightly less dense, which increases Q for the same mass flow rate.
Yes. Run each trial, then export CSV and compute mean and standard deviation. Averaging reduces random timing and sensor noise, and the spread supports uncertainty reporting.
Common causes include nonuniform velocity profiles, probe misalignment, swirl, partial pipe filling, or leaks during timed collection. Improve straight‑run length, measure velocity at multiple points, and repeat trials.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.