Calculate oil spill volume from slick size, pipe leak conditions, or tank orifice dimensions in gallons, barrels, liters, cubic feet, or m³.
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Oil Spill Volume Formula
The calculator uses a different formula for each spill scenario.
Surface slick:
V = A * t
Full pipe rupture:
V = (pi/4 * D^2 * v) * T + V_drain
Pressurized hole (pipe or tank with pressure):
V = Cd * (pi/4 * d^2) * sqrt(2 * P / rho) * T
Tank orifice with gravity head:
V = Cd * (pi/4 * d^2) * sqrt(2 * g * h) * T
Tank drain to empty:
t_drain = (2 * A_tank * sqrt(h)) / (Cd * A_hole * sqrt(2 * g))
- V = spill volume
- A = surface area of the slick
- t = average oil thickness
- D = pipe inside diameter
- d = hole or orifice diameter
- v = flow velocity in the pipe
- T = release duration
- V_drain = static line drainage after isolation
- Cd = discharge coefficient (0.62 sharp, 0.80 worn, 0.97 rounded)
- P = gauge pressure at the hole
- rho = fluid density (specific gravity x 1000 kg/m³)
- h = liquid height above the hole
- g = 9.80665 m/s²
- A_tank = horizontal cross-sectional area of the tank
The surface mode multiplies the slick area by a thickness chosen from appearance or a measured depth. The pipe mode picks between full-bore flow (area times velocity) and pressurized orifice flow, then multiplies by time and adds any line drainage. The tank mode uses Torricelli's equation, either over a fixed release time or until the tank empties.
Reference Tables
Oil appearance gives a working estimate of slick thickness when a depth measurement is not available. The values below come from Bonn Agreement and NOAA field guides.
| Appearance | Thickness | Volume per km² |
|---|---|---|
| Silvery sheen | 0.0001 mm | ~26 gal |
| Rainbow | 0.0003 mm | ~80 gal |
| Dull metallic | 0.05 mm | ~13,200 gal |
| Dark true color | 0.2 mm | ~52,800 gal |
| Dark continuous oil | 0.6 mm+ | ~158,500 gal |
Specific gravity of common petroleum products. Use these in the pressurized-hole mode.
| Product | Specific Gravity |
|---|---|
| Gasoline | 0.72 - 0.78 |
| Jet A / kerosene | 0.80 |
| Diesel / No. 2 fuel | 0.83 - 0.87 |
| Light crude oil | 0.83 - 0.87 |
| Heavy crude oil | 0.92 - 1.00 |
| Bunker C / No. 6 fuel | 0.95 - 1.03 |
Worked Examples
Example 1: Rainbow sheen on a parking lot. A spill covers a rectangle 30 ft by 20 ft and shows a rainbow appearance. Area = 600 ft² = 55.7 m². Thickness = 0.0003 mm = 3e-7 m. Volume = 55.7 × 3e-7 = 1.67e-5 m³, or about 0.0044 gallons. The visible sheen comes from a very small amount of product.
Example 2: 2-inch pipe rupture. A 2-inch (0.0508 m) line carrying diesel at 5 ft/s (1.524 m/s) ruptures and runs for 4 minutes before isolation. Pipe area = 0.00203 m². Flow = 0.00309 m³/s. Volume = 0.00309 × 240 = 0.742 m³, about 196 gallons, before line drainage.
FAQ
How accurate are sheen-based estimates? They are order-of-magnitude. Real slicks vary in thickness across their footprint, and weathered oil thickens at the edges. Use a measured average depth when you can.
Which discharge coefficient should you pick? Use 0.62 for a sharp-edged hole in steel or fiberglass, 0.80 for a corroded or eroded opening, and 0.97 for a rounded nozzle or fitted outlet.
Does the tank drain mode account for the falling liquid level? Yes. The drain-time formula integrates Torricelli flow as the head drops from h to zero, assuming a constant horizontal cross section.
Should you include line drainage? Yes, if the rupture is below significant elevated piping. After valve closure, gravity drains any product upstream of the closure down to the leak point.
