40 CFR § 1065.630 - Local acceleration of gravity.

---
identifier: "/us/cfr/t40/s1065.630"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "40 CFR § 1065.630 - Local acceleration of gravity."
title_number: 40
title_name: "Protection of Environment"
section_number: "1065.630"
section_name: "Local acceleration of gravity."
chapter_name: "ENVIRONMENTAL PROTECTION AGENCY"
subchapter_number: "U"
subchapter_name: "AIR POLLUTION CONTROLS"
part_number: "1065"
part_name: "ENGINE-TESTING PROCEDURES"
positive_law: false
currency: "2026-03-24"
last_updated: "2026-03-24"
format_version: "1.1.0"
generator: "[email protected]"
authority: "42 U.S.C. 7401-7671q."
regulatory_source: "70 FR 40516, July 13, 2005, unless otherwise noted."
cfr_part: "1065"
---


# 1065.630 Local acceleration of gravity.

(a) The acceleration of Earth's gravity, *a*<sub>g</sub>, varies depending on the test location. Determine *a*<sub>g</sub> at your location by entering latitude, longitude, and elevation data into the U.S. National Oceanographic and Atmospheric Administration's surface gravity prediction website at *https://geodesy.noaa.gov/cgi-bin/grav_pdx.prl.*

(b) If the website specified in paragraph (a) of this section is unavailable, or the test location is outside of the continental United States, you may calculate *a*<sub>g</sub> for your latitude as follows:

Where:

*u* = Degrees north or south latitude.

*u* = 45°

*a*<sub>g</sub> = 9.7803267715 · (1 + 5.2790414 ·  10<sub>−3</sub> · sin
<sup>2</sup> (45) + 2.32718 ·  10<sub>−5</sub> · sin
<sup>4</sup> (45) + 1.262 ·  10<sub>−7</sub> · sin
<sup>6</sup> (45) + 7 ·  10<sub>−10</sub> · sin
<sup>8</sup> (45)

*a*<sub>g</sub> = 9.8061992026 m/s 
<sup>2</sup>

[79 FR 23784, Apr. 28, 2014, as amended at 88 FR 4680, Jan. 24, 2023]