Road Grade Elevations on a Straight Line
Computes finished elevations along a straight vertical grade — at any station or at fixed intervals — including pavement-edge and shoulder-edge elevations from a standard crowned cross-section.
1 · How is the grade defined?
2 · Alignment data
Results
About this road grade elevation calculator
This tool works out finished road levels along a straight vertical grade — a section of profile with no vertical curve. It is aimed at highway and design engineers, road designers, site engineers and surveyors who need setting-out levels quickly, whether for land grading, gore areas, intersections, roundabouts or short tie-ins between curves.
Two ways to define the grade
- From two known points — enter Sta 1, Elev 1, Sta 2 and Elev 2,
and the grade is calculated as
G = (Elev2 − Elev1) / (Sta2 − Sta1)and shown in the Computed grade field. - From one point and a grade — enter a station, its elevation and a known grade percentage, and the profile is projected forward from there.
How elevations are computed
Along a straight grade the level at any station is
Elev = Elevref + G × (Sta − Staref).
Stations can be typed as chainage such as 1+250.50 or as plain metres.
You can return a single station, a fixed interval running to an end station, or a
start-to-end range at a chosen interval.
Cross-section levels
Switch the elevation type to Use offsets and each station also reports the edge levels of a crowned cross-section, derived outward from the centreline:
- PGL
- Profile grade line — the finished level at the road centreline.
- LPE / RPE
- Left and right pavement edge, each the PGL plus its pavement width times its cross slope.
- LSE / RSE
- Left and right shoulder edge, each the pavement edge plus its shoulder width times its shoulder cross slope.
Left and right sides are calculated independently, so unequal widths or different cross slopes either side are handled correctly. Negative cross slopes fall away from the centreline, which is the normal crowned arrangement; enter positive values where the surface rises away from the centreline, as on a superelevated section.
Straight grades versus vertical curves
This calculator covers straight grades only. Where two grades meet and a parabolic transition is required, use the vertical curve design calculator, which returns K, PVC and PVT, the middle ordinate and the high or low point, and checks the curve against stopping sight distance.
Frequently asked questions
How do you calculate road elevation at a given chainage?
On a straight grade the elevation at any station is the reference elevation plus
the grade multiplied by the distance from the reference station, or
Elev = Elevref + G × (Sta − Staref)
with the grade expressed as a decimal. This calculator applies that relationship
automatically once you supply either two known points or one point and a grade.
How is the grade between two points calculated?
The grade is the rise divided by the run, so
G = (Elev2 − Elev1) / (Sta2 − Sta1), usually expressed as
a percentage. Enter the two station and elevation pairs and the computed grade is
shown in the Computed grade field and carried through to every result.
What is the profile grade line, or PGL?
The profile grade line is the reference line the vertical alignment is designed along, normally the finished surface at the road centreline. All cross-section levels are derived from it by applying the cross slopes outward, so the PGL is the elevation the grade calculation returns before any offsets are applied.
What do PGL, LPE, LSE, RPE and RSE mean in the results?
PGL is the profile grade line at the centreline. LPE and RPE are the left and right pavement edges, and LSE and RSE are the left and right shoulder edges. Each edge elevation is the previous point plus its width multiplied by its cross slope, so the pavement edge comes off the centreline and the shoulder edge comes off the pavement edge.
How are pavement and shoulder edge elevations calculated?
The pavement edge is the centreline elevation plus the pavement width multiplied by the pavement cross slope as a decimal. The shoulder edge is then the pavement edge plus the shoulder width multiplied by the shoulder cross slope. Left and right sides are calculated independently, so different widths and slopes on each side are handled correctly.
Why are cross slopes entered as negative values?
A negative cross slope means the surface falls away from the centreline, which is the normal crowned arrangement that sheds water to both sides. The defaults of −1.50% on the pavement and −4.00% on the shoulder reflect typical practice. Enter a positive value where the surface rises away from the centreline, such as on a superelevated section.
When should I use this instead of a vertical curve calculator?
Use this tool where the profile is a single straight grade with no curve, which covers land grading, gore areas, intersections, roundabouts and short tie-ins. Where two grades meet and a parabolic curve is needed, use the vertical curve design calculator instead, which handles crest and sag curves and checks K against sight distance.
Related engineering design tools
Designing the rest of the same alignment: