diff --git a/app/filamentdb.py b/app/filamentdb.py
index e4ea1ea..a895063 100644
--- a/app/filamentdb.py
+++ b/app/filamentdb.py
@@ -1,5 +1,7 @@
 import logging
+import math
 import os
+import re
 import time
 
 import httpx
@@ -64,6 +66,70 @@ def spool_counts() -> dict[tuple[str, str], int]:
     return result
 
 
+def _parse_ams_html(html: str) -> list[dict]:
+    """
+    Parse the /ams/ HTML page to extract slot info.
+    Each card yields: slot, material, color, weight_remaining_g, roll_id (numeric).
+    """
+    slots = []
+    for card in re.split(r'class="card ams-card"', html)[1:]:
+        slot_m    = re.search(r'<h4>Slot (\d+)</h4>', card)
+        matcol_m  = re.search(
+            r'<strong>.*?</strong><br>\s*(.*?)<br>\s*(.*?)\s*</p>', card, re.DOTALL
+        )
+        weight_m  = re.search(r'~(\d+)g', card)
+        roll_id_m = re.search(r'action="/rolls/(\d+)/prints"', card)
+        if slot_m and matcol_m and weight_m and roll_id_m:
+            slots.append({
+                "slot":               int(slot_m.group(1)),
+                "material":           matcol_m.group(1).strip(),
+                "color":              matcol_m.group(2).strip(),
+                "weight_remaining_g": int(weight_m.group(1)),
+                "roll_id":            int(roll_id_m.group(1)),
+            })
+    return slots
+
+
+def get_ams_slots() -> list[dict]:
+    """Return currently loaded AMS slots (live, not cached — state changes often)."""
+    try:
+        r = httpx.get(f"{_base()}/ams/", timeout=5, verify=False)
+        r.raise_for_status()
+        return _parse_ams_html(r.text)
+    except Exception:
+        logger.warning("FilamentDB AMS endpoint unreachable")
+        return []
+
+
+def find_matching_ams_roll(material: str, color: str) -> dict | None:
+    """
+    Find the best roll in AMS1/slots 1-4 matching material+color.
+    If multiple match, pick the one with least filament remaining (use it up first).
+    """
+    matches = [
+        s for s in get_ams_slots()
+        if s["material"].lower() == material.lower()
+        and s["color"].lower() == color.lower()
+    ]
+    return min(matches, key=lambda s: s["weight_remaining_g"]) if matches else None
+
+
+def log_print_on_roll(roll_id: int, weight_g: int, note: str) -> bool:
+    """POST a print log entry to FilamentDB for the given roll."""
+    try:
+        r = httpx.post(
+            f"{_base()}/rolls/{roll_id}/prints",
+            data={"weight_used_g": weight_g, "note": note, "redirect_to": ""},
+            timeout=5,
+            verify=False,
+        )
+        r.raise_for_status()
+        return True
+    except Exception:
+        logger.warning("FilamentDB print log failed for roll %s", roll_id)
+        return False
+
+
 def available_colors(material: str | None = None) -> list[str]:
     """Unique color names in stock, optionally filtered by material."""
     rows = get_stock()
diff --git a/app/routers/ui.py b/app/routers/ui.py
index d8ae935..6cf9d2c 100644
--- a/app/routers/ui.py
+++ b/app/routers/ui.py
@@ -1,3 +1,4 @@
+import math
 import os
 import uuid as _uuid
 from datetime import datetime, timedelta
@@ -21,8 +22,9 @@ from app.models.printer_type import PrinterType
 from app.models.pricing import PricingConfig
 from app.models.todo import Todo
 from app.constants import COLORS, MATERIALS
-from app.estimation import estimate
-from app.filamentdb import available_colors, available_materials, get_stock, spool_counts
+from app.estimation import estimate  # also used in start_job
+from app.filamentdb import (available_colors, available_materials, find_matching_ams_roll,
+                             get_stock, log_print_on_roll, spool_counts)
 from app.stl import get_stl_dir, list_stl_files
 from app.stl_analysis import analyse, get_cache_map  # noqa: F401 used in job_detail route
 
@@ -325,6 +327,29 @@ def start_job(job_id: int, printer_id: int = Form(...), db: Session = Depends(ge
     printer.status = PrinterStatus.printing
 
     db.add(JobLog(job_id=job_id, message=f"Job started on {printer.name}"))
+
+    # Log filament usage against matching AMS roll in FilamentDB
+    if job.job_material and job.job_color:
+        stl = db.query(StlCache).filter_by(filename=job.file_name).first() if job.file_name else None
+        if stl and stl.volume_ccm:
+            weight_g = math.ceil(estimate(stl.volume_ccm, job.job_material)["weight_g"])
+            roll = find_matching_ams_roll(job.job_material, job.job_color)
+            if roll:
+                note = (f"POPS {job.job_uuid[:8] if job.job_uuid else job.id}: "
+                        f"{job.file_name or job.name} on {printer.name}")
+                if log_print_on_roll(roll["roll_id"], weight_g, note):
+                    db.add(JobLog(job_id=job_id, message=(
+                        f"FilamentDB: logged {weight_g} g against roll #{roll['roll_id']} "
+                        f"(AMS slot {roll['slot']} — {roll['material']} {roll['color']}, "
+                        f"{roll['weight_remaining_g']} g remaining, least-full roll selected)"
+                    )))
+                else:
+                    db.add(JobLog(job_id=job_id, message=f"FilamentDB: print log failed for roll #{roll['roll_id']}"))
+            else:
+                db.add(JobLog(job_id=job_id, message=(
+                    f"FilamentDB: no {job.job_material} {job.job_color} roll found in AMS"
+                )))
+
     db.commit()
     return RedirectResponse(url=f"/jobs/{job_id}", status_code=HTTP_303_SEE_OTHER)