Conversions Flow Rate Calculator (2024 Guide)

Convert flow rate values instantly, compare the same quantity across units, and preview engineering-friendly equivalents.
Flow rate inputs

Enter Value A and choose the unit you know; Value B updates automatically.
Value A Unit A
Value B Unit B
Converted value
—
Target unit —
L/s equivalent —
US gpm equivalent —
m³/h equivalent —
How to Use This Calculator

Provide a flow value using Value A plus the corresponding unit. The tool instantly recalculates Value B whenever you change the number or unit, keeping both sides in sync.
Click Calculate to lock in the conversion, or use inline edits with the 100ms debounce. Presets reset the form to common scenarios, and you can download the reference table after a successful calculation.
Methodology

The calculator normalizes every entry to m³/s internally and reconverts it to the selected destination unit. Equivalent outputs rely on the same base for consistent comparison.
Anchoring on m³/s prevents rounding drift across chained conversions.
Value B mirrors Value A automatically whether you type forward or backward.
Common equivalents display the same base amount in L/s, US gpm, and m³/h.
Keep track of unit families (US vs Imperial) and always confirm temperature or density assumptions if you later convert volumetric flow to mass flow.
Engineering notes

Use SI units, preserve dimensional consistency, and verify safety factors before applying conversions in designs.
Key entities: Conversions, Flow, Rate, Value A, Unit A, Value B, Unit B.
Inputs used by this calculator

Value A
Unit A
Value B
Unit B
Consistency checks

The tool enforces valid units, numerical inputs, and consistent rounding boundaries.
Full original guide (expanded)

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          <!-- Popular presets -->
          <div class="flex flex-wrap gap-2 mb-5">
            <button class="pill pill-active" data-val="10" data-unit="usgpm">10 US gpm</button>
            <button class="pill" data-val="1" data-unit="m3h">1 m³/h</button>
            <button class="pill" data-val="2.5" data-unit="lps">2.5 L/s</button>
            <button class="pill" data-val="100" data-unit="cfm">100 CFM</button>
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          <!-- Secondary panel: common equivalents -->
          <h2 class="text-lg font-semibold mb-3">Common equivalents</h2>
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            <div class="bg-gray-50 border rounded-md p-3">
              <p class="text-xs text-gray-500">L/s</p>
              <p id="out-lps" class="font-semibold text-lg">—</p>
            </div>
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              <p class="text-xs text-gray-500">US gpm</p>
              <p id="out-usgpm" class="font-semibold text-lg">—</p>
            </div>
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              <p class="text-xs text-gray-500">m³/h</p>
              <p id="out-m3h" class="font-semibold text-lg">—</p>
            </div>
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          <h2 class="text-lg font-semibold mb-3">Quick US gpm → L/s table</h2>
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                  <th class="py-1 px-2">L/s</th>
                  <th class="py-1 px-2">m³/h</th>
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          <article class="prose">
            <h2>Formulas & unit definitions</h2>
            <div class="formula-box">
              <p><strong>Base:</strong> this tool uses m³/s internally.</p>
              <ul>
                <li>1 L = 1×10<sup>−3</sup> m³</li>
                <li>1 US gal = 3.785411784 L</li>
                <li>1 Imp gal = 4.54609 L</li>
                <li>1 ft³ = 0.028316846592 m³</li>
                <li>1 in³ = 1.6387064×10<sup>−5</sup> m³</li>
              </ul>
            </div>
            <h3>Examples</h3>
            <p><strong>US gpm → L/s</strong>: L/s = gpm × 3.785411784 ÷ 60 = gpm × 0.0630901964</p>
            <p><strong>m³/h → L/min</strong>: L/min = (m³/h × 1000) ÷ 60 = m³/h × 16.6667</p>
            <h2>FAQ</h2>
            <h3>US vs Imperial gallons?</h3>
            <p>They are different by ~20%. Choose the correct gallon family (US or Imperial) in the dropdowns.</p>
            <h3>When to use L/s vs m³/h?</h3>
            <p>L/s is frequent in lab/process calculations; m³/h is common in HVAC, water, and industrial specifications.</p>
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<section class="bg-white p-4 rounded-lg shadow-md mt-6"><h2 class="text-lg font-semibold mb-2">Engineering notes</h2><p class="text-sm text-gray-700">Use SI units and keep dimensional consistency. Verify boundary conditions, safety factors, and design limits.</p><p class="text-sm text-gray-700 mt-2">Key entities: Conversions, Flow, Rate, Value A, Unit A, Value B, Unit B.</p></section><section class="bg-white p-4 rounded-lg shadow-md mt-6"><h2 class="text-lg font-semibold mb-2">Inputs used by this calculator</h2><ul class="text-sm text-gray-700 list-disc pl-5"><li>Value A</li><li>Unit A</li><li>Value B</li><li>Unit B</li></ul></section><section class="bg-white p-4 rounded-lg shadow-md mt-6"><h2 class="text-lg font-semibold mb-2">Consistency checks</h2><p class="text-sm text-gray-700">Checks: consistent units, allowed ranges, technical rounding.</p></section><section class="bg-white p-4 rounded-lg shadow-md mt-6"><h2 class="text-lg font-semibold mb-2">Engineering notes</h2><p class="text-sm text-gray-700">Use SI units and keep dimensional consistency. Verify boundary conditions, safety factors, and design limits.</p><p class="text-sm text-gray-700 mt-2">Key entities: Conversions, Flow, Rate, Value A, Unit A, Value B, Unit B.</p></section><section class="bg-white p-4 rounded-lg shadow-md mt-6"><h2 class="text-lg font-semibold mb-2">Inputs used by this calculator</h2><ul class="text-sm text-gray-700 list-disc pl-5"><li>Value A</li><li>Unit A</li><li>Value B</li><li>Unit B</li></ul></section><section class="bg-white p-4 rounded-lg shadow-md mt-6"><h2 class="text-lg font-semibold mb-2">Consistency checks</h2><p class="text-sm text-gray-700">Checks: consistent units, allowed ranges, technical rounding.</p></section><!-- %%EEAT_STRIP%% -->
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  <script>
    // ----- Units dictionary: factor to base (m^3/s) -----
    const UNITS = [
      { key: 'm3s',  label: 'm³/s',                  toBase: 1,                     fromBase: 1 },
      { key: 'm3h',  label: 'm³/h',                  toBase: 1/3600,               fromBase: 3600 },
      { key: 'lps',  label: 'L/s',                   toBase: 1e-3,                 fromBase: 1e3 },
      { key: 'lpm',  label: 'L/min',                 toBase: 1e-3/60,              fromBase: 60e3 },
      { key: 'lph',  label: 'L/h',                   toBase: 1e-3/3600,            fromBase: 3600e3 },

      { key: 'usgpm',label: 'US gpm',                toBase: 0.003785411784/60,    fromBase: 60/0.003785411784 },
      { key: 'usgps',label: 'US gal/s',              toBase: 0.003785411784,       fromBase: 1/0.003785411784 },
      { key: 'usgph',label: 'US gal/h',              toBase: 0.003785411784/3600,  fromBase: 3600/0.003785411784 },

      { key: 'imgpm',label: 'Imperial gpm',          toBase: 0.00454609/60,        fromBase: 60/0.00454609 },
      { key: 'imgps',label: 'Imperial gal/s',        toBase: 0.00454609,           fromBase: 1/0.00454609 },
      { key: 'imgph',label: 'Imperial gal/h',        toBase: 0.00454609/3600,      fromBase: 3600/0.00454609 },

      { key: 'ft3s', label: 'ft³/s',                 toBase: 0.028316846592,       fromBase: 1/0.028316846592 },
      { key: 'cfm',  label: 'ft³/min (CFM)',         toBase: 0.028316846592/60,    fromBase: 60/0.028316846592 },
      { key: 'ft3h', label: 'ft³/h',                 toBase: 0.028316846592/3600,  fromBase: 3600/0.028316846592 },

      { key: 'in3s', label: 'in³/s',                 toBase: 1.6387064e-5,         fromBase: 1/1.6387064e-5 },
      { key: 'in3m', label: 'in³/min',               toBase: 1.6387064e-5/60,      fromBase: 60/1.6387064e-5 },
      { key: 'in3h', label: 'in³/h',                 toBase: 1.6387064e-5/3600,    fromBase: 3600/1.6387064e-5 }
    ];

    const unitMap = Object.fromEntries(UNITS.map(u => [u.key, u]));

    // DOM elements
    const valA = document.getElementById('val-a');
    const unitA = document.getElementById('unit-a');
    const valB = document.getElementById('val-b');
    const unitB = document.getElementById('unit-b');

    const outLps = document.getElementById('out-lps');
    const outUSGPM = document.getElementById('out-usgpm');
    const outM3h = document.getElementById('out-m3h');

    const presetBtns = document.querySelectorAll('.pill');

    // Populate selects
    function fillOptions(sel, defaultKey) {
      UNITS.forEach(u => {
        const opt = document.createElement('option');
        opt.value = u.key;
        opt.textContent = u.label;
        if (u.key === defaultKey) opt.selected = true;
        sel.appendChild(opt);
      });
    }
    fillOptions(unitA, 'usgpm');
    fillOptions(unitB, 'lps');

    let isUpdating = false;

    function toBase(value, key) {
      const u = unitMap[key];
      return (value || 0) * u.toBase;
    }
    function fromBase(base, key) {
      const u = unitMap[key];
      return (base || 0) * u.fromBase;
    }

    function refreshSecondary(base) {
      outLps.textContent = fromBase(base, 'lps').toFixed(6);
      outUSGPM.textContent = fromBase(base, 'usgpm').toFixed(4);
      outM3h.textContent = fromBase(base, 'm3h').toFixed(4);
    }

    function updateFromA() {
      if (isUpdating) return;
      isUpdating = true;
      const a = parseFloat(valA.value || 0);
      const base = toBase(a, unitA.value);
      const b = fromBase(base, unitB.value);
      valB.value = (Math.abs(b) < 1e-4 ? b.toExponential(6) : b.toFixed(6)).replace(/0+$/,'').replace(/\.$/,'');
      refreshSecondary(base);
      isUpdating = false;
    }

    function updateFromB() {
      if (isUpdating) return;
      isUpdating = true;
      const b = parseFloat(valB.value || 0);
      const base = toBase(b, unitB.value);
      const a = fromBase(base, unitA.value);
      valA.value = (Math.abs(a) < 1e-4 ? a.toExponential(6) : a.toFixed(6)).replace(/0+$/,'').replace(/\.$/,'');
      refreshSecondary(base);
      isUpdating = false;
    }

    unitA.addEventListener('change', updateFromA);
    unitB.addEventListener('change', updateFromA);
    valA.addEventListener('input', updateFromA);
    valB.addEventListener('input', updateFromB);

    // Presets
    function setPreset(value, key) {
      valA.value = value;
      unitA.value = key;
      unitB.value = (key === 'usgpm') ? 'lps' : 'usgpm';
      updateFromA();
    }
    presetBtns.forEach(btn => {
      btn.addEventListener('click', () => {
        presetBtns.forEach(b => b.classList.remove('pill-active'));
        btn.classList.add('pill-active');
        setPreset(parseFloat(btn.dataset.val), btn.dataset.unit);
      });
    });

    // Quick table
    const tblBody = document.getElementById('tbl-body');
    function buildTable() {
      tblBody.innerHTML = '';
      [1,5,10,25,50,100].forEach(g => {
        const base = toBase(g, 'usgpm');
        const lps = fromBase(base, 'lps');
        const m3h = fromBase(base, 'm3h');
        const tr = document.createElement('tr');
        tr.innerHTML = `<td class="py-1 px-2">${g}</td>
                        <td class="py-1 px-2">${lps.toFixed(4)}</td>
                        <td class="py-1 px-2">${m3h.toFixed(3)}</td>`;
        tblBody.appendChild(tr);
      });
    }

    // init
    buildTable();
    updateFromA();
  </script>

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      tex: { inlineMath: [['\\(','\\)'], ['$', '$']], displayMath: [['$','$'], ['\\[','\\]']] },
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    var target = document.querySelector(
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        { once: true }
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  window.__cmpLoadQueued = window.__cmpLoadQueued || [];
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Formulas
Base conversions reference:
m³/s is the internal base unit for all flow comparisons.
1 L = 1×10⁻³ m³ and 1 m³ = 1000 L.
1 US gallon = 3.785411784 L, 1 Imperial gallon = 4.54609 L.
Set frequency constants: 1 h = 3600 s, 1 min = 60 s.
Conversions apply ⟨toBase⟩ and ⟨fromBase⟩ multipliers so every path uses the same m³/s intermediary, therefore preventing drift between units.
Citations
Changelog
v1.1.0 — Canonical layout adaptation with conversions hero, quick reference table, and consistent parsing logic.
v1.0.0 — Original conversions flow rate guide.
✓ Verified by Ugo Candido Last Updated: 2026-01-19 Version 1.1.0
Version 1.5.0