82 values, each with its units, its uncertainty, and where it came from.
All 351 constants →
mAbsolute roughness ε of new uncoated cast iron pipe, about 0.26 mm — five times rougher than steel, and far worse when tuberculated.
mAbsolute roughness ε of new commercial steel or wrought-iron pipe, 0.046 mm (0.00015 ft) — the Moody-chart default.
mAbsolute roughness ε of drawn copper tube, glass and smooth plastic pipe, about 0.0015 mm — 30 times smoother than steel.
PaIsothermal bulk modulus of liquid water at 20 °C and 1 atm, about 2.18 GPa — a 0.005 % volume change per bar of pressure.
PaTypical specified 28-day cylinder strength of ordinary structural concrete, about 28 MPa (4000 psi), with 20–40 MPa the usual range.
kg/m³Typical density of 6061 aluminium alloy at 20 °C, 2700 kg/m³ or 169 lb/ft³ — about 35 % of steel for the same volume.
kg/m³Density of dry air at 20 °C and 101.325 kPa, 1.204 kg/m³ — the standard-air value behind the 1.08 sensible-heat factor.
kg/m³Density of ordinary hexagonal ice at 0 °C and 1 atm, about 917 kg/m³ — roughly 8 % lighter than the water it freezes from.
kg/m³Density of liquid mercury at 20 °C and 1 atm, 13 534 kg/m³ — 13.5 times water, and the basis of the mmHg pressure unit.
kg/m³Typical density of normal-weight reinforced concrete, 2400 kg/m³ or 150 lb/ft³, including ordinary reinforcing steel content.
kg/m³Representative density of open-ocean seawater at 35 g/kg salinity and 15 °C, about 1025 kg/m³ or 64 lb/ft³ at the surface.
kg/m³Representative density of construction softwood such as spruce-pine-fir or Douglas fir at 12 % moisture, roughly 500 kg/m³.
kg/m³Typical density of carbon and low-alloy structural steel at 20 °C, 7850 kg/m³ or 490 lb/ft³, essentially independent of grade.
kg/m³998.207 kg/m³ at 20 °C and 1 atm (62.316 lb/ft³), the reference density behind specific gravity and most laboratory calibrations.
Pa·sDynamic viscosity of dry air at 20 °C and 1 atm, 18.1 µPa·s — about 1/55 of water's, though its kinematic viscosity is 15× larger.
Pa·sDynamic viscosity of a typical SAE 30 mineral engine oil at 40 °C, roughly 0.088 Pa·s — about 90 times that of water at 20 °C.
Pa·sDynamic viscosity of pure water at 20 °C and 1 atm, 1.002 mPa·s — the value that made the centipoise a de facto standard.
Ω·mResistivity of pure aluminium at 20 °C, 2.65 × 10⁻⁸ Ω·m; EC-grade 1350 conductor is about 2.83 × 10⁻⁸ Ω·m (61 % IACS).
Ω·mResistivity of plain carbon steel at 20 °C, roughly 1.4–1.8 × 10⁻⁷ Ω·m — about ten times copper's, and composition-sensitive.
Ω·mResistivity of pure annealed copper at 20 °C, 1.678 × 10⁻⁸ Ω·m; the commercial IACS reference is 1.7241 × 10⁻⁸ Ω·m.
—Total hemispherical emissivity of flat black paint near room temperature, about 0.96 — the practical stand-in for a black body.
—Total emissivity of oxidised or mill-scaled carbon steel, about 0.8 — against roughly 0.1 for the same steel polished bright.
—Total hemispherical emissivity of bright polished aluminium near room temperature, about 0.05 — an excellent radiant barrier.
—Representative static friction coefficient for clean dry steel on steel, about 0.6 with a legitimate range of 0.4 to 0.8.
—Representative friction coefficient for oil-lubricated steel on steel in boundary lubrication, about 0.10 (range 0.05–0.15).
—Representative peak friction coefficient for a passenger tyre on dry asphalt, about 0.8 — competition tyres exceed 1.0.
—Representative friction coefficient for a passenger tyre on wet asphalt, about 0.5, falling to 0.3 or below on worn tyres.
—Hazen-Williams roughness coefficient for aged unlined cast iron pipe, typically 100 — new pipe is near 130, badly tuberculated near 60.
—Hazen-Williams roughness coefficient for smooth plastic pipe such as PVC, PE and CPVC, conventionally taken as 150 for design.
J/kg333.55 kJ/kg (143.4 BTU/lb) to melt ice at 0 °C without changing its temperature — equivalent to 80 K of sensible heating of water.
J/kg2256.4 kJ/kg (970 BTU/lb) to boil water at 100 °C and 1 atm, nearly seven times the heat of fusion and the basis of all steam heating.
—Manning roughness coefficient for finished concrete channels and pipe, typically 0.013 with a defensible range of 0.011 to 0.016.
kg/m³Water is densest at about 3.98 °C, 999.975 kg/m³ — the anomaly that makes ice float and keeps deep lakes from freezing solid.
KWater boils at 99.9743 °C (373.1243 K) under one standard atmosphere — very slightly below 100 °C, and not by accident.
—Poisson's ratio of wrought aluminium alloys in the elastic range, about 0.33 — slightly higher than steel's 0.30.
—Poisson's ratio of hardened normal-weight concrete under service compression, typically 0.15–0.25 with 0.20 used in design.
—Poisson's ratio of natural and synthetic rubber, about 0.499 — nearly incompressible, the practical limit for isotropic solids.
—Poisson's ratio of carbon and alloy steel in the elastic range, 0.30 — the lateral contraction per unit of axial extension.
—Typical maximum relative permeability of commercial soft iron — a wildly variable figure spanning roughly 200 to 5000 with purity and field level.
—Typical relative permeability of annealed mu-metal in weak fields — the nickel-iron alloy used to shield instruments from stray magnetic fields.
—Typical dielectric constant of dry air at 0 °C and one atmosphere — so close to vacuum that most capacitor and antenna work ignores the difference.
—Typical dielectric constant of FR-4 circuit-board laminate near 1 GHz — the number behind every microstrip impedance and trace-delay calculation.
—Typical dielectric constant of PTFE (Teflon), about 2.1 and almost flat from DC to tens of gigahertz — the benchmark low-loss RF insulator.
—Typical static dielectric constant of liquid water at 20 °C — an outlier among common liquids and the reason water dissolves salts so well.
PaShear modulus of common wrought aluminium alloys at room temperature, about 26 GPa or 3800 ksi — one third of steel's value.
PaShear (rigidity) modulus of structural steel at room temperature, 77.2 GPa or 11 200 ksi — the value used in torsion and shear.
—Specific gravity of the mineral solids in most soils, about 2.65 for quartz sands and 2.70–2.75 for clays — remarkably consistent.
J/(kg·K)About 2108 J/(kg·K) for ice at 0 °C, roughly half the value for liquid water — the reason freezers cool loads far faster than they freeze them.
J/(kg·K)4181.6 J/(kg·K) for liquid water at 25 °C and 0.1 MPa — about 1.00 BTU/(lb·°F), the highest of any common liquid.
J/(kg·K)Specific heat of a 30 % by volume propylene glycol/water mix near 40 °C, about 3850 J/(kg·K) — some 8 % below plain water.
J/(kg·K)Specific heat of plain carbon steel near room temperature, about 486 J/(kg·K) or 0.116 BTU/(lb·°F), rising with temperature.
m/sSpeed of sound in dry air at 20 °C and 1 atm, 343 m/s or 1125 ft/s — set by temperature, essentially not by pressure.
m/sLongitudinal (bulk) wave speed in carbon steel, about 5900 m/s; the thin-bar wave speed √(E/ρ) is lower, near 5100 m/s.
m/sSpeed of sound in fresh water at 20 °C and 1 atm, about 1482 m/s — 4.3 times faster than in air, and rising with temperature.
1/KTemperature coefficient of resistance for annealed copper referenced to 20 °C, 0.00393 per kelvin — 0.393 % more resistance per degree.
PaMinimum ultimate tensile strength of an SAE Grade 5 bolt up to 1 in diameter, 120 ksi or 827 MPa, with 85 ksi proof strength.
PaMinimum ultimate tensile strength of an SAE Grade 8 bolt, 150 ksi or 1034 MPa, with 130 ksi proof — the high-strength shop fastener.
W/(m·K)Thermal conductivity of dry air at 20 °C and 1 atm, about 0.026 W/(m·K) — the benchmark every insulation is measured against.
W/(m·K)Thermal conductivity of pure aluminium at 25 °C, about 237 W/(m·K); alloy 6061-T6 is markedly lower at roughly 167 W/(m·K).
W/(m·K)Thermal conductivity of plain carbon steel near room temperature, roughly 50 W/(m·K) — about an eighth of copper's value.
W/(m·K)Thermal conductivity of normal-weight structural concrete, roughly 1.4–2.0 W/(m·K) depending on aggregate and moisture content.
W/(m·K)Thermal conductivity of pure annealed copper at 25 °C, about 401 W/(m·K) — the benchmark for practical heat-transfer materials.
W/(m·K)Thermal conductivity of standard fibreglass batt at 24 °C, about 0.040 W/(m·K) — roughly R-3.6 per inch in US units.
W/(m·K)Aged thermal conductivity of rigid polyisocyanurate or XPS board, roughly 0.024–0.029 W/(m·K), about R-5 to R-6 per inch.
W/(m·K)Thermal conductivity of Type 304 austenitic stainless steel at 20 °C, about 16 W/(m·K) — roughly a third of carbon steel's.
W/(m·K)Thermal conductivity of liquid water at 20 °C and 1 atm, about 0.60 W/(m·K) — high for a liquid, still 700× worse than copper.
1/KLinear expansion coefficient of aluminium near room temperature, 23.4 µm/(m·K) or 13 µin/(in·°F) — twice that of steel.
1/KLinear thermal expansion coefficient of carbon steel near room temperature, 11.7 µm/(m·K) or 6.5 µin/(in·°F).
1/KLinear expansion coefficient of normal-weight concrete, roughly 8–12 µm/(m·K) — close enough to steel to make reinforcing work.
1/KLinear expansion coefficient of copper near room temperature, 16.8 µm/(m·K) or 9.3 µin/(in·°F) — 44 % more than steel.
1/KLinear expansion coefficient of rigid PVC pipe, about 54 µm/(m·K) or 3.0 µin/(in·°F) — nearly five times that of steel.
1/KLinear expansion coefficient of Type 304 austenitic stainless steel, 17.3 µm/(m·K) — about 50 % more than carbon steel.
N/m³Typical moist bulk unit weight of loose sand, about 15.5 kN/m³ or 99 lbf/ft³; dense sand runs nearer 19.5 kN/m³.
N/m³Typical saturated unit weight of soft normally consolidated clay, about 16 kN/m³ or 102 lbf/ft³, with 14–18 kN/m³ the usual range.
PaSaturation vapour pressure of water at 20 °C, 2339 Pa (0.339 psia) — the absolute pressure at which 20 °C water boils.
PaTypical 0.2 % offset yield strength of 6061-T6 aluminium, 276 MPa or 40 ksi, with an ultimate tensile strength near 310 MPa.
PaSpecified minimum yield strength of ASTM A36 structural steel, 36 ksi or 248 MPa — a floor guaranteed by the mill, not a measurement.
PaSpecified minimum yield strength of ASTM A992 wide-flange steel, 50 ksi or 345 MPa — the default grade for W-shapes since 1998.
PaElastic modulus of 6061 aluminium at room temperature, 68.9 GPa or 10 000 ksi — roughly one third the stiffness of steel.
PaSecant elastic modulus of 28 MPa (4000 psi) normal-weight concrete, about 25 GPa — computed from strength, not measured directly.
PaElastic modulus of carbon and low-alloy structural steel at room temperature, 200 GPa or 29 000 ksi, effectively grade-independent.
PaElastic modulus of annealed Type 304 austenitic stainless steel at 20 °C, about 193 GPa or 28 000 ksi — 3 % below carbon steel.
