Vertical Curve Calculator

Your details

Grade of the approach tangent. Positive = uphill, negative = downhill.
%
Grade of the departure tangent. Positive = uphill, negative = downhill.
%
Horizontal length of the vertical curve, measured from PVC to PVT.
ft
Chainage / station of the point of vertical intersection (PVI).
ft
Elevation of the point of vertical intersection (PVI).
ft
Any station between PVC and PVT whose curve elevation you want to check.
ft
Used only to look up the AASHTO minimum K-value for design compliance. Leave at 0 to skip the check.
mph
K-valueSag curve
120ft/%

Horizontal distance (ft or m) required for a 1% change in grade.

Grade difference (A)5%
Curve typeSag (valley)
PVC station700ft
PVC elevation109ft
PVT station1,300ft
PVT elevation106ft
High/low point station1,060ft
High/low point elevation103.6ft
Elevation at target station103.75ft
AASHTO K complianceMeets AASHTO minimum (K >= 96)
Minimum K required96
PVC elevation109
High/Low point elev.103.6
PVT elevation106
Target station elev.103.75

K = 120.0: Sag (valley) over 600 ft

  • Grade changes from -3% to 2% over 600 ft, giving an algebraic difference of 5.00%.
  • The low point is at station 1060.0 ft, elevation 103.600 ft.
  • Meets AASHTO minimum (K >= 96)
  • For sag curves, headlight sight distance at night is the governing criterion. Comfort-based and drainage checks may set a higher minimum length than the stopping sight distance formula alone.

Next stepReview the elevation profile chart below to confirm the curve fits your vertical alignment constraints, then check the high/low point drainage if K > 167 ft/%.

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