LDT to IES Converter

This LDT to IES converter turns an EULUMDAT (.ldt) photometric file into the IESNA LM-63 (.ies) format that North American lighting design tools, e-commerce platforms, and product feeds expect. Paste or drop a file and get a clean, downloadable IES output in seconds — useful for distributors normalizing photometric data inherited from European suppliers.

What it checks

Before and during conversion, the tool validates the structure of your source file and the integrity of the output so you do not ship a photometric file that silently fails downstream:

• Format detection — confirms the input is a valid EULUMDAT LDT file (the fixed line-numbered header, lamp block, and intensity table) rather than a mislabeled IES, XML, or CSV file.
• Geometry mapping — reads the number of C-planes (Mc) and the gamma angles per plane (Ng) and maps them to the IES TILT, vertical, and horizontal angle arrays.
• Photometric type — translates the EULUMDAT symmetry indicator into the correct IES photometric type and angle ranges so a symmetric luminaire is not exported as if it were asymmetric.
• Unit and multiplier handling — converts luminous intensity values (cd/1000lm in LDT) into absolute candela using the declared lamp lumens, and sets the IES candela multiplier accordingly.
• Luminaire dimensions — carries over length, width, and height into the IES luminous-dimensions line, converting millimeters to meters where required.
• Output integrity — checks that the generated IES file parses cleanly: keyword block, tilt line, and a complete intensity matrix with no missing or NaN values.

How the LDT to IES converter works

EULUMDAT (LDT) and IESNA LM-63 (IES) both describe the same physical thing — how much light a luminaire emits in every direction — but they encode it differently. LDT is a strict line-positional format common in Europe; IES is a keyword-and-array format standard in North America. Converting between them means parsing the LDT intensity table indexed by C-plane and gamma angle, rescaling intensities from the per-1000-lumen convention to absolute candela, and re-emitting the same distribution in the IES angle and keyword structure.

1. 1
   Parse the LDT header
   Read the fixed lines for manufacturer, symmetry, plane count, angle count, lamp lumens, and luminaire geometry.
2. 2
   Rebuild the intensity grid
   Map each C-plane and gamma angle to its candela value, applying the lumen-based multiplier.
3. 3
   Emit IES LM-63
   Write the keyword block, TILT=NONE line, angle arrays, and candela matrix in valid LM-63 order.
4. 4
   Re-validate
   Parse the output back to confirm it is a well-formed IES file before you download it.

Everything runs client-side in your browser. Your photometric files are never uploaded to a server, which matters when you are handling pre-release supplier data under NDA. The same normalization problem shows up across catalogs: a furniture supplier sends dimensions in millimeters while your PIM expects inches, an MRO vendor ships specs as PDFs, a CPG feed mislabels units. Photometric conversion is one instance of the broader enrichment work of making heterogeneous supplier data conform to one canonical shape — which is exactly what Claro’s product data enrichment platform automates across an entire catalog with provenance on every transformed value.

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