How this calculator works
Direct variation is a straight-line relationship through the origin. Multiplying x by a factor multiplies y by the same factor when k is fixed. Finding k or x requires dividing, so a zero divisor cannot produce a unique answer. A known zero k is allowed when calculating y.
Formula
y = kx; x = y/k; k = y/x.
Worked example
With k = 3 and x = 4, y = 12. With x = 5 and y = -15, the proportionality constant is -15/5 = -3.
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Frequently asked questions
Can the values be negative?
Yes. Signs are preserved in the multiplication and division, and the constant may be negative.
Are physical units converted?
No. Enter values in units consistent with the equation. The units of k depend on the units used for x and y.
Why is a zero denominator rejected?
Division by zero cannot determine a finite unique value. Supply a non-zero independent value or constant as required by the selected mode.