Calculator
Example Data Table
| Use Case | Original Value | W/m² | mW/cm² | Btu/h·ft² |
|---|---|---|---|---|
| Peak solar reference | 1000 W/m² | 1000 | 100 | 317.00 |
| Lab lamp test | 25 mW/cm² | 250 | 25 | 79.25 |
| High intensity beam | 0.05 W/cm² | 500 | 50 | 158.50 |
| Thermal load study | 80 W/ft² | 861.11 | 86.11 | 273.13 |
Formula Used
Base conversion: EW/m² = input value × source unit factor.
Target conversion: target value = EW/m² ÷ target unit factor.
Lux option: EW/m² = lux ÷ luminous efficacy.
Foot-candle option: EW/m² = foot-candle × 10.7639104167 ÷ luminous efficacy.
Radiant power: P = E × A, where area is entered in square meters.
Energy dose: H = E × t, where time is entered in seconds.
How to Use This Calculator
Enter one value in the single value field. Select the original unit and the target unit. Add luminous efficacy only when lux or foot-candle is used. Enter area when you need total radiant power. Enter exposure time when you need energy dose. Use batch values for many readings. Press calculate to show results above the form. Use CSV for spreadsheet work. Use PDF for a quick report.
Irradiance Conversion Guide
What Irradiance Means
Irradiance is radiant power received by a surface. It is normally written as watts per square meter. Engineers use it for solar panels. Lab teams use it for lamps. Designers use it for heat studies. The value links power, area, and exposure. A higher value means more radiant energy reaches each square meter.
Why Unit Conversion Matters
Different industries use different units. Solar reports often use W/m². Optical testing may use mW/cm². Thermal documents may use Btu/h·ft². A small unit change can create a large numeric change. This calculator reduces that risk. It converts every input through W/m² as a common base. That keeps the method clear.
Working With Area
Irradiance alone does not show total power. Area must also be known. A lamp delivering 200 W/m² over one square meter gives 200 watts. The same irradiance over five square meters gives 1000 watts. This is useful for panels, curing beds, heating zones, and test chambers.
Working With Exposure Time
Exposure time turns irradiance into radiant dose. Dose is important in curing, material aging, UV studies, and solar exposure checks. The calculator multiplies W/m² by seconds. The result is joules per square meter. It also shows joules per square centimeter for compact lab records.
Lux and Foot-Candle Notes
Lux and foot-candle are lighting units. They describe visible light response. They are not pure radiant units. A luminous efficacy value is required. The default is only an estimate. Use a measured or specified lm/W value when accuracy matters. This is especially important for LEDs, lamps, and filtered sources.
Best Practice
Use consistent units across every project. Record source unit, target unit, area, time, and luminous efficacy. Keep exported files with test notes. This makes audits easier. It also makes repeated calculations safer.
FAQs
What is irradiance?
Irradiance is radiant power arriving on a surface per unit area. The common unit is W/m². It is widely used in solar, optical, lighting, and thermal calculations.
What is the base unit used here?
The calculator converts values through W/m². This base makes conversions consistent between metric, imperial, laboratory, and radiation exposure units.
Can I convert mW/cm² to W/m²?
Yes. One mW/cm² equals 10 W/m². Enter your value, select mW/cm² as the source unit, and choose W/m² as the target unit.
Why is luminous efficacy needed?
Lux and foot-candle depend on human visual response. Luminous efficacy links visible light output to radiant power. Without it, conversion to irradiance is only an estimate.
What does area calculate?
Area calculates total radiant power. The calculator multiplies irradiance by square meters. The result is watts across the entered surface area.
What does exposure time calculate?
Exposure time calculates energy dose. The calculator multiplies irradiance by seconds. It reports dose in J/m² and J/cm².
Can I convert many readings together?
Yes. Enter batch values separated by spaces, commas, semicolons, or new lines. The calculator processes up to 100 values in one submission.
What exports are available?
You can download CSV results for spreadsheets. You can also create a PDF report from the displayed result section after calculation.