Calculate TMC water volume from cubic feet, MCM, acre-feet, gallons, flow over time, or area and depth, and reverse-solve flow, duration, area, or depth.
- All Miscellaneous Calculators
- Cubic Feet to Pounds Calculator
- Cubic Feet to Tons Calculator
- Water Volume Calculator
- Liquid Volume Calculator
- Pipe Volume Calculator
TMC Formula
TMC stands for thousand million cubic feet (1 TMC = 1,000,000,000 ft³ = 28,316,846.592 m³). The calculator uses one of three volume relationships, with an explicit solve mode for each inverse.
Unit conversion
Flow rate × duration
Area × depth
- V — volume in cubic metres
- Q — average flow rate in cusecs (ft³/s)
- t — duration in days (86,400 seconds each)
- A — surface area in m²
- d — mean depth or rainfall in metres
Inputs in other units (cumecs, L/s, acres, hectares, mm, etc.) are converted to SI before the formula is applied. The flow formula assumes a constant average rate. Area × mean depth is a first-pass volume estimate requiring an appropriate mean depth; a varying reservoir geometry may need a capacity curve. Rainfall over a catchment gives gross precipitation volume, not captured runoff. Evaporation, seepage and conveyance losses are excluded.
Reference Tables
Common TMC equivalents in other water-volume units (rounded where shown):
| From | Equals |
|---|---|
| 1 TMC | 1,000,000,000 ft³ |
| 1 TMC | 28.317 MCM (million m³) |
| 1 TMC | 28.317 billion litres |
| 1 TMC | 22,957 acre-feet |
| 1 TMC | ≈11,574.074074 cusec-days |
| 1 cusec for 1 day | 0.0000864 TMC |
| 10,000 cusecs for 1 day | 0.864 TMC |
Days required to release 1 TMC at a steady flow:
| Flow rate | Time for 1 TMC |
|---|---|
| 1,000 cusecs | 11.6 days |
| 5,000 cusecs | 2.3 days |
| 10,000 cusecs | 1.16 days (~28 hours) |
| 25,000 cusecs | 11.1 hours |
| 50,000 cusecs | 5.6 hours |
| 100,000 cusecs | 2.8 hours |
Worked Examples
Example 1 — release from a dam. A spillway discharges 15,000 cusecs for 5 days. Cusec-days = 15,000 × 5 = 75,000. TMC = 75,000 × 0.0000864 = 6.48 TMC.
Example 2 — rainfall over a catchment. 80 mm of rain falls on a 500 km² basin. Volume = 500,000,000 m² × 0.080 m = 40,000,000 m³. TMC = 40,000,000 ÷ 28,316,846.592 ≈ 1.41 TMC. This is gross rainfall volume before runoff and other losses.
Example 3 — reservoir capacity check. A reservoir holds 5 TMC. In MCM that is 5 × 28.316846592 = 141.58423296 MCM (about 141.6 MCM), or about 114,784 acre-feet.
FAQ
Is TMC the same as TMC ft? Yes. TMC, TMCft, and tmcft all mean thousand million cubic feet (10⁹ ft³).
Why does cusec-day matter? Reservoir releases are reported in cusecs. Multiplying cusecs by days gives cusec-days, and exactly 312,500/27 cusec-days (approximately 11,574.074074) equals 1 TMC.
Can I use this for irrigation planning? Use it for gross volume accounting; it does not estimate runoff or irrigation collection efficiency, and it does not account for evaporation, seepage, or conveyance losses.
