Formulas
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The exact formula behind each Calcumatix calculator. See how we choose and test them on our methodology page.
Percentage Calculator
The tool uses three percent formulas, one for each mode.
Fraction Calculator
For two fractions a/b and c/d, the calculator uses these formulas.
Average Calculator
Mean formula: add all values, then divide by the count. Median method: sort the list, then take the middle value. If the list has two middle values, add those two values and divide by two. Range formula: take the largest value and subtract the smallest value.
Age Calculator
Age is counted by moving from the birth date to the target date in whole calendar units. The calculator counts full years, then full months, then leftover days. Total days equals the number of calendar midnights between the two dates.
Date Duration Calculator
The calculator compares the earlier date with the later date. It counts full calendar years, then full calendar months, then remaining days. Total days is the exact day count between the dates, and total weeks equals total days / 7.
BMI Calculator
BMI uses one ratio of weight to height, with a conversion factor for imperial units.
BMR Calculator
The calculator uses the Mifflin-St Jeor equation. Male metric formula: BMR = 10 x weight kg + 6.25 x height cm - 5 x age + 5. Female metric formula: BMR = 10 x weight kg + 6.25 x height cm - 5 x age - 161.
TDEE Calculator
TDEE = BMR x activity factor. BMR uses the Mifflin-St Jeor equation. The calculator then applies the selected activity factor: sedentary 1.2, light 1.375, moderate 1.55, active 1.725, or extra active 1.9.
Loan Calculator
The fixed payment formula is M = P x r x (1 + r)^n / ((1 + r)^n - 1).
Compound Interest Calculator
Future value of principal: A = P x (1 + r / n)^(n x t). With contribution C at the end of each compounding period, contribution value = C x (((1 + r / n)^(n x t) - 1) / (r / n)).
Percentage of Goal Calculator
Current value means the amount reached so far. Goal value means the full target. Both values must use the same unit, such as dollars, steps, gifts, points, hours, or tasks. A goal value of zero has no valid percent result because the math would divide by zero.
Audiobook Percentage Calculator
Elapsed time means how much audio has already played. Total time means the full length of the audiobook, podcast, or recording. The calculator converts hours and minutes before dividing, so 2 hours 30 minutes becomes 150 minutes.
Attendance Percentage Calculator
Sessions attended means the number marked present. Total sessions means every counted session in the attendance period. The total must include attended and missed sessions, and the total sessions value must be greater than zero.
Vote Percentage Calculator
Votes for option means the number of valid votes received by one choice. Total valid votes means the full valid vote count used as the base. The total valid votes value must be greater than zero, and votes for one option should not exceed the total valid votes.
Shooting Percentage Calculator
Shots made means the number of successful shots in the group. Shots attempted means every counted shot attempt in that same group. Field goal percentage uses field goals made as shots made and field goal attempts as shots attempted. The NBA glossary lists two point field goal percentage as 2FGM / 2FGA and three point percentage as 3PM / 3PA, which follows the same made divided by attempted pattern.
Hockey Goalie Save Percentage Calculator
Saves means shots on goal that the goalie stopped. Shots faced means the total shots on goal against that goalie. Hockey box scores usually display the result as a three decimal value, so 0.917 is written as .917 rather than 91.7%.
Volleyball Hitting Percentage Calculator
Kills means attacks that score directly. Errors means attacks that give the opponent a point. Total attacks means kills plus errors plus zero attacks, which are attacks kept in play by the defense.
Labor Percentage Calculator
Use staff cost and sales from the same date range. Staff cost can include pay, tax, benefits, and other labor items if your books include them. Total sales should match the same period.
Food Cost Percentage Calculator
Food cost should match the cost line used in your records. Food sales should cover the same period. Keep drinks, tax, fees, and tips out unless your books include them in food sales.
Ownership Percentage Calculator
Owned units are the units held by one owner. Total units are the units in the same pool. Do not mix common shares with preferred shares or voting units with non-voting units unless your records say to do so.
Percentage Rent Increase Calculator
Old rent is the rent before the change. New rent is the proposed or new rent. Compare the same pay period, such as monthly rent with monthly rent. Old rent must be greater than zero.
BPS to Percentage Calculator
A basis point is a unit for rate points. It is not the dollar effect of a rate change. To find a dollar effect, you also need principal, time, fees, and payment terms.
Year Over Year Percentage Calculator
Current value is the newer period. Prior value is the matching older period. The prior value must be greater than zero. Use the same metric in both periods.
Percentage by Weight Calculator
Part mass means the weighed amount of the solute, ingredient, or material. Total mass means the full weighed amount of the mix or solution. The result is w/w%, also written as weight by weight percent or mass by mass percent. Use one unit for both mass fields before you calculate. If one value is in grams and the other is in milligrams, convert one value first.
Percentage of Volume Calculator
Part volume means the measured amount of the liquid or gas part. Total volume means the final measured amount of the whole mix. The result is v/v%, also written as volume by volume percent. Use one unit for both fields before you calculate. Do not place a mass value into a volume field.
Dilution Calculator
C1 means stock strength. V1 means stock volume used. C2 means target strength after dilution. V2 means final volume after solvent is added. Use one strength basis for C1 and C2, such as percent with percent or molarity with molarity, and one volume unit for V1 and V2.