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Calcimator

NOTAM Impact Assessment Calculator

Assess flight plan impact from TFRs, runway closures, navaid outages, and altitude restrictions.

About this calculator

NOTAMs rarely cancel a flight outright, but they quietly stack up time, fuel, and cost — this calculator adds up four common disruption types so you can see the combined effect before you launch. Route deviations around TFRs or restricted areas multiply your per-deviation detour distance by the number of deviations, converting that extra distance into extra time and fuel at your planned groundspeed and burn rate. A closed destination runway is modeled as a full extra leg to your alternate (its own distance, time, and fuel), and a navaid outage adds a flat extra-approach-time penalty (for a hold or a different, less efficient procedure) converted into fuel at your burn rate.

An altitude restriction is handled differently: if the TFR or airspace caps you below your planned cruise altitude, the calculator applies a fuel penalty of 5% per 2,000 feet you're forced down, reflecting the real efficiency loss of cruising lower and thicker. All of these are summed into total additional time, fuel, and dollar cost, plus a 0–100 impact severity score that weights time delay up to 40 points, fuel penalty up to 30, a closed runway at a flat 20, and a navaid outage at 10 — so a single runway closure alone can already push the score into "notably disruptive" territory. The scoring weights and penalty rates are reasonable planning heuristics, not FAA-published figures, so use the score to compare scenarios relative to each other rather than as an absolute regulatory measure.

Inputs

ft

Results

Impact severity (0-100)

11

Additional time (min)

10

Revised distance (NM)320
Additional fuel (gal)1.7
Additional cost ($)$10.83
Total deviation (NM)20
Alternate fuel (gal)0
Altitude fuel penalty (%)0
How to Use This Calculator
  1. Enter planned route distance (NM), groundspeed (kts), and fuel burn (GPH).
  2. Set detour distance per TFR (NM) and number of airspace deviations required.
  3. Indicate whether the primary destination runway is closed.
  4. Review impact severity score (0–100), additional flight time (min), extra fuel burned, and extra cost ($).
  5. Use the output to decide whether to file an alternate route, delay the flight, or accept the penalty.

How the result changes with Planned distance (NM)

Planned distance (NM)Impact severity (0-100)Additional time (min)
1502110
2251410
450710
750410

What each input means

Planned distance (NM)
Original planned route distance.
Groundspeed (kts)
Expected groundspeed for time/fuel estimates.
Fuel burn (GPH)
Cruise fuel consumption rate.
Deviation per TFR (NM)
Extra distance per TFR or restricted area deviation.
Number of deviations
How many TFRs or restricted areas require routing around.
Primary runway closed (0/1)
1 if the primary runway at destination is NOTAMed closed.
Alternate distance (NM)
Distance to alternate airport if primary runway closed.
Navaid outage (0/1)
1 if a navaid needed for the approach is out of service.
Extra approach time (min)
Additional time for alternate approach procedure.
Altitude restriction (ft)
Max altitude allowed by TFR (0 = no restriction).
Planned cruise alt (ft)
Originally planned cruising altitude.
Fuel price ($/gal)
Cost per gallon for additional fuel cost.

What each result means

Impact severity (0-100)
Overall NOTAM impact score. Higher = more disruptive.
Revised distance (NM)
Total route distance including deviations.
Additional time (min)
Total extra time due to all NOTAM impacts.
Additional fuel (gal)
Total extra fuel required for deviations and alternates.
Additional cost ($)
Dollar cost of the extra fuel.
Total deviation (NM)
Total extra distance from all route deviations.
Alternate fuel (gal)
Extra fuel for diversion to alternate airport.
Altitude fuel penalty (%)
Percentage fuel increase from flying at a lower altitude.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Planned distance (NM) = 300, Groundspeed (kts) = 120, Fuel burn (GPH) = 10, Deviation per TFR (NM) = 20 = 12 input(s) provided
  2. Calculate Impact severity
    Impact severity
    11 = 11
  3. Calculate Additional time
    Additional time = deviationTimeMin + alternateTimeMin + navaidAdditionalMin
    10 = 10
  4. Calculate Revised distance
    Revised distance = plannedDistanceNm + totalDeviationNm
    320 = 320
  5. Calculate Additional fuel
    Additional fuel = deviationFuel + alternateFuel + navaidAdditionalFuel + altitudePenaltyFuel
    1.7 = 1.7

Engine last updated . Checked against 3 independently-derived tests — how we verify calculators. Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.

Frequently Asked Questions

How does a runway closure factor into the impact score if I don't enter fuel and time for the alternate directly?

When "Primary runway closed" is set to 1, the calculator automatically computes a full extra leg to your entered alternate — its own distance, time, and fuel at your same groundspeed and burn rate — and adds a flat 20 points to the impact score. You don't need to add alternate fuel into any other field; the calculator handles it internally once the closure flag is set.

Why does an altitude restriction increase fuel burn but not flight time?

The model treats altitude restrictions purely as an efficiency penalty — 5% more fuel per 2,000 feet you're forced below planned cruise altitude, applied to your planned-leg fuel — without changing the flight-time calculation, since flying lower doesn't itself change groundspeed or route distance in this model. Real lower-altitude flying can also change true airspeed and winds, which this simplified model doesn't capture.

What exactly goes into the 0–100 impact score?

It's a weighted sum of four components: additional time versus planned time (up to 40 points), additional fuel versus planned fuel (up to 60 but capped at 30), a flat 20 points if the runway is closed, and a flat 10 points for a navaid outage, with the total capped at 100. It's meant for comparing NOTAM scenarios against each other, not as an official FAA disruption rating.

If I have multiple TFRs to route around, how do I enter them?

Enter the typical extra distance for one deviation in "Deviation per TFR (NM)" and the count of separate deviations in "Number of deviations" — the calculator multiplies the two to get total deviation distance, then converts that into extra time and fuel. If your deviations vary significantly in size, use an average detour distance across all of them for the most representative result.

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