Grade Rod Calculator and Tenths to Inches Chart
Shooting grade with a laser or a builder’s level and a rod read in feet, tenths and hundredths? Enter the benchmark and backsight to get the HI and grade rod, then every rod reading becomes a cut or fill. Work out what to mark on a grade stake, convert tenths to inches, and print a pocket card.
The math, shown transparently
No black box. These are the formulas the calculator runs on every keystroke. Every input is in feet.
// Level and rod (USACE, NRCS, Local 49)
HI = benchmark elevation + backsight
grade_rod = HI - design grade elevation (can be negative)
ground_elevation = HI - rod reading
cut_fill = grade_rod - rod reading (+ = CUT, - = FILL)
// Grade stake
design_at_hub = reference grade + offset × cross_slope% / 100
cut_fill = hub elevation - design_at_hub (+ = CUT, - = FILL)
rod_at_grade = hub rod + cut, or hub rod - fill
// Converter (1 ft = 12 in exactly)
inches = feet × 12
nearest 1/8 in = feet × 96 eighths, rounded half up
feet = inches ÷ 12, rounded half up to 0.01 ft
Cut/fill is rounded to 0.01 ft, the precision Caltrans marks most stakes to (slope, abutment fill and rough grade stakes go to 0.1 ft), and its inches are that rounded number converted, so they match the chart. Inches to the nearest 1/8 is our display choice, labeled wherever it appears.
The design-at-hub line is our own algebra, not a quote. Caltrans marks a cross slope as the rise or fall in feet per 100 feet, plus or minus going out from the stationing line, and SCDOT calculates it as the difference in elevation divided by the width. Solve that for the difference in elevation over your offset and you get offset × slope% ÷ 100.
Worked examples
Example values to check the method by hand, not defaults. Benchmark 100.00, backsight 5.32, design grade 98.50:
HI = 100.00 + 5.32 = 105.32
grade_rod = 105.32 - 98.50 = 6.82
rod 6.40: 6.82 - 6.40 = +0.42 = CUT 0.42 ft
check: ground = 105.32 - 6.40 = 98.92, above grade
0.42 × 12 = 5.04 in; 0.42 × 96 = 40.32 eighths, nearest 40 = 5 in
rod 7.55: 6.82 - 7.55 = -0.73 = FILL 0.73 ft
check: ground = 105.32 - 7.55 = 97.77, below grade
0.73 × 12 = 8.76 in; 0.73 × 96 = 70.08 eighths, nearest 70 = 8 3/4 in
NRCS’s own example works the same way: HI 249.3 and planned grade 243.0 give a grade rod of 6.3; a foresight of 9.8 gives 6.3 - 9.8 = -3.5, a fill, and 5.1 gives 6.3 - 5.1 = +1.2, a cut. (NRCS’s text prints 5.8 in the first subtraction; 9.8 is the reading that gives its -3.5, so that is what we show.)
A hub 12.00 ft out from a reference line with design grade 101.00, cross slope -2.0% (falls going out):
design_at_hub = 101.00 + 12.00 × (-2.0 / 100) = 101.00 - 0.24 = 100.76
hub 101.36: 101.36 - 100.76 = +0.60, mark C 0.60
0.60 × 12 = 7.20 in; 0.60 × 96 = 57.60 eighths, nearest 58 = 7 1/4 in
hub 100.50: 100.50 - 100.76 = -0.26, mark F 0.26
0.26 × 12 = 3.12 in; 0.26 × 96 = 24.96 eighths, nearest 25 = 3 1/8 in
at +2.0% (rises going out): design_at_hub = 101.00 + 0.24 = 101.24
hub 101.36: 101.36 - 101.24 = +0.12, mark C 0.12
0.12 × 12 = 1.44 in; 0.12 × 96 = 11.52 eighths, nearest 12 = 1 1/2 in
To turn a stake into a rod target, Local 49’s formula sheet adds a cut to the rod reading on the hub and subtracts a fill. Its example stake reads F 1.56 to finish grade with the rod reading 5.06 on the hub: 5.06 - 1.56 = 3.50 at finish grade.
Tenths to inches chart
Hundredths of a foot to inches, rounded to the nearest 1/8 inch. Find the tenth across the top and the hundredth down the side: 0.42 ft is column 0.4, row +.02, 5 in. Exact inches are feet × 12; no cell is more than 0.06 in off the exact value. The pocket card PDF in the calculator prints this same chart on 3 3/4 × 2 3/4 in cards.
| ft | 0.0 | 0.1 | 0.2 | 0.3 | 0.4 | 0.5 | 0.6 | 0.7 | 0.8 | 0.9 |
|---|---|---|---|---|---|---|---|---|---|---|
| +.00 | 1 1/4 | 2 3/8 | 3 5/8 | 4 3/4 | 6 | 7 1/4 | 8 3/8 | 9 5/8 | 10 3/4 | |
| +.01 | 1/8 | 1 3/8 | 2 1/2 | 3 3/4 | 4 7/8 | 6 1/8 | 7 3/8 | 8 1/2 | 9 3/4 | 10 7/8 |
| +.02 | 1/4 | 1 1/2 | 2 5/8 | 3 7/8 | 5 | 6 1/4 | 7 1/2 | 8 5/8 | 9 7/8 | 11 |
| +.03 | 3/8 | 1 1/2 | 2 3/4 | 4 | 5 1/8 | 6 3/8 | 7 1/2 | 8 3/4 | 10 | 11 1/8 |
| +.04 | 1/2 | 1 5/8 | 2 7/8 | 4 1/8 | 5 1/4 | 6 1/2 | 7 5/8 | 8 7/8 | 10 1/8 | 11 1/4 |
| +.05 | 5/8 | 1 3/4 | 3 | 4 1/4 | 5 3/8 | 6 5/8 | 7 3/4 | 9 | 10 1/4 | 11 3/8 |
| +.06 | 3/4 | 1 7/8 | 3 1/8 | 4 3/8 | 5 1/2 | 6 3/4 | 7 7/8 | 9 1/8 | 10 3/8 | 11 1/2 |
| +.07 | 7/8 | 2 | 3 1/4 | 4 1/2 | 5 5/8 | 6 7/8 | 8 | 9 1/4 | 10 1/2 | 11 5/8 |
| +.08 | 1 | 2 1/8 | 3 3/8 | 4 1/2 | 5 3/4 | 7 | 8 1/8 | 9 3/8 | 10 1/2 | 11 3/4 |
| +.09 | 1 1/8 | 2 1/4 | 3 1/2 | 4 5/8 | 5 7/8 | 7 1/8 | 8 1/4 | 9 1/2 | 10 5/8 | 11 7/8 |
| ft | 0.0 | 0.1 | 0.2 | 0.3 | 0.4 |
|---|---|---|---|---|---|
| +.00 | 1 1/4 | 2 3/8 | 3 5/8 | 4 3/4 | |
| +.01 | 1/8 | 1 3/8 | 2 1/2 | 3 3/4 | 4 7/8 |
| +.02 | 1/4 | 1 1/2 | 2 5/8 | 3 7/8 | 5 |
| +.03 | 3/8 | 1 1/2 | 2 3/4 | 4 | 5 1/8 |
| +.04 | 1/2 | 1 5/8 | 2 7/8 | 4 1/8 | 5 1/4 |
| +.05 | 5/8 | 1 3/4 | 3 | 4 1/4 | 5 3/8 |
| +.06 | 3/4 | 1 7/8 | 3 1/8 | 4 3/8 | 5 1/2 |
| +.07 | 7/8 | 2 | 3 1/4 | 4 1/2 | 5 5/8 |
| +.08 | 1 | 2 1/8 | 3 3/8 | 4 1/2 | 5 3/4 |
| +.09 | 1 1/8 | 2 1/4 | 3 1/2 | 4 5/8 | 5 7/8 |
| ft | 0.5 | 0.6 | 0.7 | 0.8 | 0.9 |
|---|---|---|---|---|---|
| +.00 | 6 | 7 1/4 | 8 3/8 | 9 5/8 | 10 3/4 |
| +.01 | 6 1/8 | 7 3/8 | 8 1/2 | 9 3/4 | 10 7/8 |
| +.02 | 6 1/4 | 7 1/2 | 8 5/8 | 9 7/8 | 11 |
| +.03 | 6 3/8 | 7 1/2 | 8 3/4 | 10 | 11 1/8 |
| +.04 | 6 1/2 | 7 5/8 | 8 7/8 | 10 1/8 | 11 1/4 |
| +.05 | 6 5/8 | 7 3/4 | 9 | 10 1/4 | 11 3/8 |
| +.06 | 6 3/4 | 7 7/8 | 9 1/8 | 10 3/8 | 11 1/2 |
| +.07 | 6 7/8 | 8 | 9 1/4 | 10 1/2 | 11 5/8 |
| +.08 | 7 | 8 1/8 | 9 3/8 | 10 1/2 | 11 3/4 |
| +.09 | 7 1/8 | 8 1/4 | 9 1/2 | 10 5/8 | 11 7/8 |
Cells are inches. Cut/fill = grade rod - ground rod. Plus = CUT, minus = FILL.
Sources and assumptions
- Height of instrument and elevations. HI = benchmark elevation + backsight; elevation = HI - foresight: USACE EM 1110-1-1005, para 3-13a, p. 3-28 (archived copy); NRCS Engineering Field Handbook, ch. 1 Surveying (2022), Height of instrument, p. 650-1.74; IUOE Local 49 Training Center, Student Workbook 2023, Grades & Stakes Formulas, p. 1. The USACE manual is linked as an archived copy because the official site refuses automated checks.
- Grade rod and the cut/fill sign. Grade rod = HI - planned grade, plus or minus; ground rod subtracted from grade rod, minus is a fill and plus a cut: NRCS Engineering Field Handbook, ch. 1 Surveying (2022), Use of Grade Rod, p. 650-1.84; WSDOT Highway Surveying Manual M 22-97, ch. 15, Philadelphia rod example, p. 15-21; IUOE Local 49 Training Center, Student Workbook 2023, Grades & Stakes Formulas, p. 1. The same Local 49 sheet works a Lenker (direct-elevation) rod the other way round, ground rod - grade rod, so the sign flips on a Lenker. WSDOT calls the Lenker the ideal rod for setting grade hubs because it reads the elevation directly, with no grade rod to compute: WSDOT Highway Surveying Manual M 22-97, ch. 15, §15-08.1, p. 15-21. This calculator assumes a standard rod.
- Rods and lasers. Rods graduated in metric or in feet, tenths and hundredths (this tool is feet only), and reading a rod with a laser receiver: NRCS Engineering Field Handbook, ch. 1 Surveying (2022), Level Rods, p. 650-1.41; NRCS Engineering Field Handbook, ch. 1 Surveying (2022), Laser Levels, p. 650-1.43.
- Stakes. Cuts and fills measured from the stake’s reference point (top of hub), marked to 0.01 ft, and grade above the hub marked as a fill (F0.02 for 0.02 ft above): Caltrans Surveys Manual, ch. 12 Construction Surveys, §12.4, p. 12-21; Caltrans Surveys Manual, ch. 12 Construction Surveys, §12.4-1, p. 12-25; Caltrans Surveys Manual, ch. 12 Construction Surveys, §12.5-6 Final Grade Stakes, p. 12-38. These are one state DOT’s formats, given as an example; your stakes may be marked differently.
- Cross slope. Percent rise or fall per 100 ft, signed going out from the line, and elevation difference over width: Caltrans Surveys Manual, ch. 12 Construction Surveys, §12.4, p. 12-22; SCDOT Supplemental Specification, Cross Slope Verification, §3.2. The offset formula is our rearrangement of that definition. There is no default cross slope: enter the one on your plans.
- Inches. 12 in = 1 ft exactly: NIST Handbook 44 (2026), Appendix C, p. C-5. Rounding feet to the hundredth, half up, and 1/8 in as 0.01 ft: IUOE Local 49 Training Center, Student Workbook 2023, Converting a Basic Inch to Tenths and Practice Converting Fractions, p. 9. Showing inches to the nearest 1/8 is our choice (half up, so 1/16 in shows as 1/8).
- Survey foot. NIST and NOAA, 85 FR 62698 (2020), Deprecation of the U.S. Survey Foot; 85 FR 62698, Counterpoints to Feedback Expressing Opposition, item 5, FR p. 62705. The 0.00002 ft on a 10 ft rod is our arithmetic from the 2 parts per million.
- Two-peg test. WSDOT Highway Surveying Manual M 22-97, ch. 10, p. 10-3; NRCS Engineering Field Handbook, ch. 1 Surveying (2022), Dumpy level, p. 650-1.54; NRCS Engineering Field Handbook, ch. 1 Surveying (2022), Electronic and self-leveling equipment, p. 650-1.57.
- Every field starts blank: there are no default elevations, rod readings, offsets or slopes. The numbers in the worked examples are examples only.
Frequently asked questions
How do you convert tenths of a foot to inches?
Multiply by 12. A foot is exactly 12 inches (NIST Handbook 44), so 0.1 ft = 1.2 in and 0.01 ft = 0.12 in. 0.42 ft × 12 = 5.04 in. For the nearest 1/8 inch, multiply feet by 96 (eighths per foot) and round: 0.42 × 96 = 40.32, so 40 eighths, which is 5 in. Going back, divide inches by 12: 8 1/4 in ÷ 12 = 0.6875 ft, or 0.69 ft to the hundredth.
Is 1/8 inch the same as 0.01 ft?
Close, but not the same. 1/8 in is 0.0104 ft, and 0.01 ft is 0.12 in, 0.005 in short of 1/8. The IUOE Local 49 training workbook rounds 1/8 in to 0.01 ft. Counting one eighth per hundredth gives the true nearest 1/8 up to 0.12 ft (1 1/2 in), then drifts: 0.13 ft is 1.56 in, which rounds to 1 1/2 in, not 1 5/8. Past 0.12 ft, use the chart.
Is a tenth 1 3/16 inch?
No. A tenth of a foot is exactly 1.2 in. 1 3/16 in is 1.1875 in, 0.0125 in short per tenth, so ten of them make 11 7/8 in instead of a 12 in foot, 1/8 in short. Rounded to the nearest 1/8, a tenth is 1 1/4 in (1.2 × 8 = 9.6, so 10 eighths). Rod tenths are 0.1 ft by definition; 1 3/16 is 1.2 in rounded to the nearest 1/16, not the definition.
How do I read a grade rod?
A grade rod in feet is graduated in feet, tenths and hundredths of a foot (NRCS). Read the foot, then the tenth, then count the hundredths: 6.40 is 6 feet, 4 tenths, 0 hundredths. With a laser, slide the receiver up or down the rod until it signals it is centered in the laser plane, then read the rod (NRCS). Compare the reading to the grade rod: a reading bigger than the grade rod means the ground is below grade (fill); smaller means it is above grade (cut). That is a standard rod, numbered up from its foot. On a Lenker or direct-elevation rod the numbers run the other way, so the sign flips: Local 49’s formula sheet works a Lenker as ground rod - grade rod, minus a fill and plus a cut. If your rod reads in feet, inches and eighths, use the inches side of the converter.
How do I figure the grade rod?
Read the rod on a benchmark (the backsight) and add it to the benchmark elevation to get the height of instrument: 100.00 + 5.32 = HI 105.32. Then grade rod = HI - design grade elevation: 105.32 - 98.50 = 6.82 (NRCS). That is what the rod reads with its foot on grade. For each shot, cut/fill = grade rod - rod reading: 6.82 - 6.40 = +0.42, a cut of 0.42 ft. If the HI is below grade, the grade rod is negative (NRCS writes it like -8.3 feet) and the same subtraction still works.
What does C 0.42 on a stake mean?
Cut 0.42 ft: grade is 0.42 ft below the top of the hub, which is 5 in to the nearest 1/8 (5.04 in). F means fill, grade above the hub; in Caltrans’s final grade stake example the stake reads F0.02 where the surface is 0.02 ft above the reference point. Caltrans measures cuts and fills from the stake’s reference point and marks them to the nearest hundredth of a foot, except slope stakes, abutment fill stakes and rough grade stakes, which go to the nearest tenth. A stake says what it is cut to (finish grade, subgrade), so read the stake.
What is the two-peg test?
A field check for collimation error, a level whose line of sight is not truly level. WSDOT’s surveying manual has its crews run it at the beginning and end of each day’s leveling and record it in the notes. NRCS’s field handbook gives it for the dumpy level: set two pegs 200 to 300 feet apart, set the level midway between them, and read the rod on each peg. NRCS says self-leveling equipment, laser levels and total stations can be tested using the same methods as levels, and that field adjustments should not be attempted unless the manufacturer recommends them.
US survey foot vs international foot: does it matter for rod work?
No. NIST and NOAA deprecated the US survey foot on December 31, 2022; since January 1, 2023 the US survey foot should not be used, and the international foot, 0.3048 m exactly, supersedes it (85 FR 62698). The two differ by about 2 parts per million, which the notice calls too small to be of practical consequence for the vast majority of boundary determinations. On a 10 ft rod that is 0.00002 ft, 500 times smaller than the 0.01 ft a rod is read to.
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