About the High-Low Method Calculator
This high-low method calculator separates a mixed (semi-variable) cost — such as utilities, maintenance, delivery or a phone plan — into its fixed and variable components. Paste one line per period with the activity level and the total cost; the calculator picks the periods with the highest and lowest activity, works out the variable cost per unit from the slope between them, and backs out the fixed cost.
It is aimed at managerial and cost accounting students, small-business owners building a budget and analysts who need a quick cost formula (total cost = fixed cost + variable rate × activity). Enter a planned activity level to estimate the total cost for a future month or a flexible budget.
The high-low method uses only two data points, so an unusual month at either extreme can distort the result. The chart compares every actual cost with the fitted line so you can spot outliers; for a more robust estimate use regression across all points.
With the default inputs, the variable cost per unit is $9.9091. Change any value above to recalculate instantly.
How to use the high-low method calculator
- 1List each period on its own line as activity level and total cost (a label first is optional).
- 2Check that the activity measure really drives the cost, such as machine hours for maintenance.
- 3Enter the activity level you want to budget for.
- 4Read the variable rate, fixed cost and estimated total cost.
- 5Check the chart for outliers before relying on the formula.
Formula and method
The high-low method assumes total cost is a straight line: a fixed amount a plus a variable rate b per unit of activity. It chooses the periods with the highest and lowest activity level (not the highest and lowest cost), and the change in cost between them divided by the change in activity gives the variable cost per unit, b.
Substituting b back into either point gives the fixed cost a (the high point and low point give the same answer). The resulting formula estimates cost at any activity level X within the relevant range. Because it relies on just two observations, it is quick but sensitive to outliers; least-squares regression uses every data point.
- b
- Variable cost per unit of activity
- a
- Fixed cost per period
- X
- Activity level (units, hours, miles…)
Worked examples
Six months of utility costs
The high point is April (2,000 units, $28,100) and the low point is March (900 units, $17,200). The $10,900 cost difference over 1,100 units gives $9.909 per unit. Fixed cost is $28,100 − 2,000 × 9.909 = $8,281.82, so 1,500 units should cost about $23,145.
Delivery van costs by miles
Between 500 and 1,200 miles, cost rises $2,100, or $3.00 per mile. Fixed cost is $6,300 − 1,200 × $3 = $2,700, so a 1,000-mile month is estimated at $5,700.
Factory maintenance by machine hours
Q3 has the most hours (6,000) and Q1 the fewest (3,000). The $24,000 cost difference over 3,000 hours is $8 per hour, leaving $37,000 fixed. At 7,000 hours the estimate is $93,000 — note this is above the observed range, so treat it with care.
Frequently asked questions
Do I pick the highest and lowest cost or the highest and lowest activity?+
Always the highest and lowest activity level. The cost driver is the independent variable, so the extremes of activity define the line, even if a different period happens to have the highest or lowest cost.
What is a mixed cost?+
A mixed or semi-variable cost has a fixed part that is paid regardless of activity and a variable part that rises with activity — for example a utility bill with a standing charge plus a per-kWh rate.
What are the limitations of the high-low method?+
It uses only two data points, so an unusual period at either extreme can distort the variable rate and fixed cost. It also assumes a straight-line relationship and is only reliable within the range of activity observed.
How is the high-low method different from regression?+
Least-squares regression fits the line through all data points and minimises total error, so it is more accurate. The high-low method is faster and easier to do by hand, which is why it is popular in exams and quick budgets.
Can fixed cost come out negative?+
Yes, if the data are not linear or the high or low point is an outlier. A negative fixed cost is a sign to check the data or use regression instead.