Calculate Running Weighted Average

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Calculate Running Weighted Average Fast

Use this focused tool to calculate running weighted average instantly and keep your data, finance, and performance metrics aligned without manual spreadsheets.

Running Weighted Average Calculator

This tool lets you calculate running weighted average by combining your current weighted average with the next data point in real time.

Existing weighted average before adding the new observation.
Sum of weights already accumulated (must be positive).
Value of the incoming data point you want to include.
Importance or frequency assigned to the new value (must be positive).
New running weighted average
0.00
Formula: (current average × current weight + new value × new weight) ÷ total weight
Combined weighted sum: 0.00
Updated total weight: 0.00
New value share of weight: 0.00%
Difference from previous average: 0.00
Running weighted average components
Component Value Weight Weighted contribution
Existing data 0.00 0.00 0.00
New data 0.00 0.00 0.00
Total after update 0.00 0.00 0.00

Weight vs Weighted Contribution

Weight Weighted contribution

Chart shows how the weight and weighted contribution of the existing set and the new value influence the running weighted average.

What is calculate running weighted average?

The phrase calculate running weighted average refers to the process of updating an average while respecting different weights for each data point. Professionals calculate running weighted average when datasets grow continuously and each observation carries a distinct importance. Analysts, portfolio managers, pricing teams, and operations leads calculate running weighted average to keep rolling metrics aligned with real-time inputs. A common misconception is that calculate running weighted average is the same as a simple mean; in reality, calculate running weighted average multiplies each value by its weight and normalizes by total weight, so high-weight items sway the result.

calculate running weighted average Formula and Mathematical Explanation

To calculate running weighted average, start with your current weighted average A0 and current total weight W0. When a new value v with weight w arrives, you calculate running weighted average using the formula:

Running weighted average = (A0 × W0 + v × w) ÷ (W0 + w)

This formula lets you calculate running weighted average without storing every past observation. It keeps the cumulative weighted sum S0 = A0 × W0, adds the new weighted contribution v × w, and divides by the new total weight. Each variable ensures you calculate running weighted average accurately while respecting importance.

Variables Table

Variables used to calculate running weighted average
VariableMeaningUnitTypical range
A0Existing weighted averageUnit of measureAny real number
W0Existing total weightWeight units> 0
vNew valueUnit of measureAny real number
wNew weightWeight units> 0
S0Existing weighted sum (A0×W0)Unit×WeightDepends on data
A1Updated running weighted averageUnit of measureAny real number

Practical Examples (Real-World Use Cases)

Example 1: A portfolio manager must calculate running weighted average return for two tranches. The current weighted average return is 6.8% with a total weight of 200 basis-weighted units. A new tranche yields 8.2% with weight 40. They calculate running weighted average: combined weighted sum = 6.8×200 + 8.2×40 = 1360 + 328 = 1688. Total weight = 240. Running weighted average = 1688 ÷ 240 = 7.033%. This calculate running weighted average step shows how a higher-yield tranche lifts the overall return moderately.

Example 2: A procurement lead wants to calculate running weighted average unit cost. Current weighted average cost is 14.50 with weight 500 units purchased. A new batch costs 13.00 with weight 120. To calculate running weighted average, combine 14.50×500 = 7250 and 13.00×120 = 1560; sum is 8810. Total weight is 620. The running weighted average cost = 8810 ÷ 620 = 14.21. Even though the new batch is cheaper, the calculate running weighted average remains close to the prior figure because existing weight dominates.

How to Use This calculate running weighted average Calculator

  1. Enter the current weighted average in the first field to calculate running weighted average from a reliable baseline.
  2. Fill in the current total weight so the tool can calculate running weighted average correctly.
  3. Add the new value and assign its weight; the calculator will instantly calculate running weighted average.
  4. Review the highlighted result and intermediate metrics to interpret how the new entry shifts the trend.
  5. Use the Copy Results button to document how you calculate running weighted average for audit trails.

Reading results is straightforward: if the new value exceeds the current average and weight is meaningful, the calculate running weighted average will rise; the opposite holds when the new value is lower.

Key Factors That Affect calculate running weighted average Results

Several forces shape how you calculate running weighted average:

  • Relative weight size: Larger new weights make the calculate running weighted average move faster.
  • Value gap: The distance between new value and current average drives the direction of the calculate running weighted average change.
  • Data volatility: Highly variable inputs mean each update when you calculate running weighted average can swing outcomes.
  • Measurement units: Consistency of units ensures you calculate running weighted average without scaling errors.
  • Timing cadence: Frequent updates require disciplined workflows to calculate running weighted average accurately under time pressure.
  • Data quality: Clean values and sensible weights prevent noise when you calculate running weighted average.
  • Fees or adjustments: If applied, they should be included before you calculate running weighted average to avoid bias.
  • Inflation or drift: Long-run datasets may need normalization before you calculate running weighted average for comparability.

Frequently Asked Questions (FAQ)

Is calculate running weighted average different from a cumulative average?

Yes, calculate running weighted average respects weights, while a cumulative average treats every data point equally.

Can I calculate running weighted average with zero weight?

No, weights must be positive; zero weight would not change the total and leads to division issues when you calculate running weighted average.

How often should I calculate running weighted average?

Calculate running weighted average whenever new weighted data arrives to keep metrics current.

What if my data includes negative values?

You can still calculate running weighted average as long as weights remain positive; negative values simply affect the weighted sum.

Can this method handle very large weights?

Yes, you can calculate running weighted average with large weights; just ensure numerical precision in your system.

Does order matter when I calculate running weighted average?

No, only sums and total weights matter; order does not change the calculate running weighted average result.

How do I interpret the weight share?

Weight share shows how much influence the new entry has when you calculate running weighted average; higher share means bigger movement.

Can I back out the prior average from the running figure?

If you know the new value, new weight, and total weight, you can algebraically reverse to calculate running weighted average components.

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Use this page to calculate running weighted average anytime you need fast, defensible updates.

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'' : vCurrentAverage.message; document.getElementById("errorCurrentWeight").innerText = vCurrentWeight.valid ? '' : vCurrentWeight.message; document.getElementById("errorNewValue").innerText = vNewValue.valid ? '' : vNewValue.message; document.getElementById("errorNewWeight").innerText = vNewWeight.valid ? '' : vNewWeight.message; if (!vCurrentAverage.valid || !vCurrentWeight.valid || !vNewValue.valid || !vNewWeight.valid) { return; } var currentAverage = vCurrentAverage.value; var currentWeight = vCurrentWeight.value; var newValue = vNewValue.value; var newWeight = vNewWeight.value; if (currentWeight === 0 || newWeight === 0) { document.getElementById("errorCurrentWeight").innerText = currentWeight === 0 ? 'Weight must be greater than zero.' : ''; document.getElementById("errorNewWeight").innerText = newWeight === 0 ? 'Weight must be greater than zero.' : ''; return; } var weightedSumExisting = currentAverage * currentWeight; var weightedSumNew = newValue * newWeight; var combinedWeightedSum = weightedSumExisting + weightedSumNew; var combinedWeight = currentWeight + newWeight; var runningAverage = combinedWeightedSum / combinedWeight; var delta = runningAverage – currentAverage; var weightShare = (newWeight / combinedWeight) * 100; document.getElementById("resultMain").innerText = runningAverage.toFixed(4); document.getElementById("combinedSum").innerText = combinedWeightedSum.toFixed(4); document.getElementById("totalWeight").innerText = combinedWeight.toFixed(2); document.getElementById("weightShare").innerText = weightShare.toFixed(2) + '%'; document.getElementById("deltaAverage").innerText = delta.toFixed(4); document.getElementById("tableCurrentAvg").innerText = currentAverage.toFixed(4); document.getElementById("tableCurrentWeight").innerText = currentWeight.toFixed(2); document.getElementById("tableCurrentContribution").innerText = weightedSumExisting.toFixed(4); document.getElementById("tableNewValue").innerText = newValue.toFixed(4); document.getElementById("tableNewWeight").innerText = newWeight.toFixed(2); document.getElementById("tableNewContribution").innerText = weightedSumNew.toFixed(4); document.getElementById("tableResult").innerText = runningAverage.toFixed(4); document.getElementById("tableTotalWeight").innerText = combinedWeight.toFixed(2); document.getElementById("tableCombinedSum").innerText = combinedWeightedSum.toFixed(4); drawChart(currentWeight, newWeight, weightedSumExisting, weightedSumNew); } function resetCalc() { document.getElementById("currentAverage").value = 72.5; document.getElementById("currentWeight").value = 120; document.getElementById("newValue").value = 80; document.getElementById("newWeight").value = 30; document.getElementById("errorCurrentAverage").innerText = ''; document.getElementById("errorCurrentWeight").innerText = ''; document.getElementById("errorNewValue").innerText = ''; document.getElementById("errorNewWeight").innerText = ''; updateCalc(); } function copyResults() { var main = document.getElementById("resultMain").innerText; var sum = document.getElementById("combinedSum").innerText; var weight = document.getElementById("totalWeight").innerText; var share = document.getElementById("weightShare").innerText; var delta = document.getElementById("deltaAverage").innerText; var text = 'Running weighted average: ' + main + '\nCombined weighted sum: ' + sum + '\nTotal weight: ' + weight + '\nNew weight share: ' + share + '\nDelta from prior average: ' + delta; if (navigator.clipboard && navigator.clipboard.writeText) { navigator.clipboard.writeText(text); } } function drawChart(weightExisting, weightNew, contribExisting, contribNew) { var canvas = document.getElementById("chartCanvas"); if (!canvas.getContext) { return; } var ctx = canvas.getContext("2d"); ctx.clearRect(0, 0, canvas.width, canvas.height); var padding = 60; var chartWidth = canvas.width – padding * 2; var chartHeight = canvas.height – padding * 2; var weights = [weightExisting, weightNew]; var contributions = [contribExisting, contribNew]; var maxVal = 0; for (var i = 0; i maxVal) { maxVal = weights[i]; } if (contributions[i] > maxVal) { maxVal = contributions[i]; } } if (maxVal === 0) { maxVal = 1; } var categories = ['Existing', 'New']; var barWidth = chartWidth / (categories.length * 3); ctx.strokeStyle = '#d3d9e4'; ctx.lineWidth = 1; for (var g = 0; g <= 5; g++) { var y = padding + (chartHeight / 5) * g; ctx.beginPath(); ctx.moveTo(padding, y); ctx.lineTo(padding + chartWidth, y); ctx.stroke(); var valueLabel = (maxVal – (maxVal / 5) * g).toFixed(0); ctx.fillStyle = '#6c7a89'; ctx.font = '12px Arial'; ctx.fillText(valueLabel, 20, y + 4); } for (var j = 0; j < categories.length; j++) { var xBase = padding + j * (barWidth * 3) + barWidth; var heightWeight = (weights[j] / maxVal) * chartHeight; var heightContribution = (contributions[j] / maxVal) * chartHeight; ctx.fillStyle = '#004a99'; ctx.fillRect(xBase, padding + chartHeight – heightWeight, barWidth, heightWeight); ctx.fillStyle = '#28a745'; ctx.fillRect(xBase + barWidth + 8, padding + chartHeight – heightContribution, barWidth, heightContribution); ctx.fillStyle = '#0c1b33'; ctx.font = '13px Arial'; ctx.fillText(categories[j], xBase, padding + chartHeight + 18); } } window.onload = function() { updateCalc(); };

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