Use this estimator for educational physics analysis, quick planning, and technique comparisons. It does not replace calibrated dosimetry, manufacturer data, or clinical judgment.
Calculator
Formula Used
1) Tube load:
mAs = mA × (time in ms / 1000)
2) Estimated air kerma at 1 meter:
Air Kerma at 1 m = Output Constant × (kVp / 80)² × Waveform Factor × Filtration Factor × mAs
3) Entrance air kerma:
Entrance Air Kerma = Air Kerma at 1 m × (100 / SSD)² × Grid Factor × AEC Factor × Repeat Count
4) Entrance skin dose:
Entrance Skin Dose = Entrance Air Kerma × Backscatter Factor
5) Dose area product:
DAP = Entrance Air Kerma in Gy × Beam Area in cm²
6) Effective dose:
Effective Dose = DAP × Conversion Coefficient × Age Factor
These formulas are practical estimation models. Real systems depend on calibration, filtration design, beam quality, patient habitus, anatomy, detector response, and facility protocols.
How to Use This Calculator
- Select a calculation method.
- Choose an exam preset or keep custom values.
- Enter age band and beam field size.
- For technique mode, fill kVp, mA, time, filtration, output, and distance.
- For DAP mode, enter measured or estimated DAP.
- Adjust backscatter, grid, AEC, and repeat settings when relevant.
- Click the calculate button to show the result above the form.
- Review the table, graph, and export buttons for reporting.
Example Data Table
| Exam | kVp | mAs | SSD (cm) | Field Size (cm) | DAP (Gy·cm²) | Effective Dose (mSv) |
|---|---|---|---|---|---|---|
| Chest PA | 110 | 2.5 | 180 | 35 × 43 | 0.12 | 0.017 |
| Abdomen AP | 80 | 20 | 100 | 35 × 43 | 2.10 | 0.546 |
| Pelvis AP | 75 | 16 | 100 | 35 × 43 | 1.80 | 0.522 |
| Lumbar Spine AP | 85 | 25 | 100 | 30 × 40 | 3.00 | 0.780 |
| Extremity AP | 55 | 2 | 100 | 18 × 24 | 0.05 | 0.00025 |
These sample values are illustrative and should not be treated as universal clinical references.
FAQs
1) What does this calculator estimate?
It estimates tube load, entrance air kerma, entrance skin dose, DAP, and effective dose using exposure settings or a known DAP value.
2) Is effective dose the same as skin dose?
No. Skin dose reflects local energy deposited near the surface. Effective dose is a weighted whole-body risk indicator based on anatomy and sensitivity factors.
3) Why does distance matter so much?
Dose changes with the inverse square law. Increasing source-to-skin distance reduces intensity rapidly, while shorter distances raise entrance dose sharply.
4) What is DAP?
DAP means dose area product. It combines beam intensity and exposed area, making it useful for comparing total beam delivery across different field sizes.
5) Why include a backscatter factor?
Backscatter accounts for radiation scattered back toward the skin from the patient and nearby material. It raises skin dose above entrance air kerma.
6) When should I use DAP mode?
Use DAP mode when your system, meter, or report already provides dose-area product. It is helpful for quick effective-dose estimation workflows.
7) Can this replace a calibrated dosimeter?
No. It is a planning and educational estimator. Acceptance testing, quality assurance, and patient-specific verification require calibrated instruments and local protocols.
8) Why is there an age factor?
Different age groups have different radiosensitivity assumptions in simplified risk modeling. The factor helps scale effective dose estimates for comparison.