Turn Rate Calculator
Turn rate means three different things, and mixing them up is the usual mistake. For a driver or pilot it is how fast heading changes, in degrees per second, through a curve. For a retailer it is how many times stock sells out and is replaced. This calculator covers all three: vehicle turn rate from speed and turn radius, aviation turn rate from bank angle and true airspeed, and inventory turnover from cost of goods sold and inventory values.
Vehicle safety limits are the tool’s built-in values, not official safety ratings for any vehicle. The banking adjustment is the tool’s own approximation, explained in the banking section below.
Quick Answer
Vehicle: 60 mph through a 45 ft bend gives 112.05 deg/sec, 1.9556 rad/s, a 3.2 second full turn and 5.35G, past a car's grip limits. Aviation: 120 knots at 15 degrees of bank gives 2.44 deg/sec, 0.81 times the standard rate. Inventory: $500,000 of cost of goods sold against $60,000 average inventory gives 8.33 turns, one full turn every 43.8 days. All three are pre-filled in their tabs.
Key takeaways
- Vehicle turn rate is speed divided by radius. Halve the radius and the turn rate doubles; double the speed and it doubles too.
- Aviation turn rate is 1091 times tan(bank angle) divided by true airspeed in knots. Steeper bank speeds the turn, faster airspeed slows it.
- Inventory turnover is cost of goods sold divided by average inventory. Days sales of inventory is 365 divided by that turnover.
- The vehicle safety check and the banking adjustment are the tool's own built-in values. Treat them as a rough flag, not a safety certification.
- Quick Answer
- How to use the turn rate calculator
- Formulas: vehicle, aviation and inventory
- Worked examples: one per mode
- Vehicle safety check: the tool's built-in limits
- Banking angle: what the tool actually does with it
- What competing calculators miss
- Other meanings of turn rate
- Frequently asked questions
- Add This Calculator to Your Website
- References
How to use the turn rate calculator
Pick the tab first, because each tab calculates something different and the Calculate button runs only the visible tab. Results stay hidden until you calculate, and switching tabs clears the previous result.
- Vehicle mode: enter speed and its unit, turn radius and its unit, and vehicle type. Add a banking angle or your own g-force limit only if you have one. Click Calculate for turn rate, radians per second, full-turn time, centripetal acceleration, g-force, turn circumference and the safety check.
- Aviation mode: enter true airspeed in knots and bank angle in degrees. The bank angle must be greater than zero and less than 90, or the tool rejects it. Click Calculate for the turn rate, the full-turn time and the multiple of the standard 3 deg/sec rate turn.
- Inventory mode: enter cost of goods sold and beginning and ending inventory values. Inventory values must not be negative, and their average must be greater than zero. Click Calculate for average inventory, turnover and days sales of inventory.
- Compare or copy: in vehicle mode, switch Method to "Compare to 3 deg/sec standard rate" to append the standard-rate multiple to the headline. Copy or share from the buttons inside the results box after any calculation.
Invalid inputs get a plain message, not a silent zero. A missing or zero speed gives "Please enter a valid speed." A missing or zero radius gives "Please enter a valid turn radius." A bank angle of 90 or more gives "Bank angle must be less than 90 degrees." An inventory average of zero gives "Average inventory must be greater than zero."
Formulas: vehicle, aviation and inventory
Three formulas, one per tab, and each one is short enough to check by hand. The vehicle and aviation formulas share the same physics underneath, while the inventory formula is a business ratio that happens to share the name.
Aviation: turn rate (deg/sec) = 1091 × tan(bank angle) ÷ true airspeed in knots. Full-turn time = 360 ÷ turn rate. Standard-rate multiple = turn rate ÷ 3.
Inventory: average inventory = (beginning inventory + ending inventory) ÷ 2. Turnover = cost of goods sold ÷ average inventory. Days sales of inventory = 365 ÷ turnover.
The aviation constant 1091 is not a magic number. It is the conversion that falls out of the level-turn relation, turn rate equals gravity times tan(bank) divided by speed, when speed is expressed in knots and the answer is wanted in degrees per second. The FAA handbook states the standard rate itself as 3 degrees per second, a full 360 degree turn in 2 minutes, and gives the pilot rule of thumb for the bank angle needed: divide true airspeed by 10 and add 7. At 120 knots that rule gives 19 degrees of bank for a standard rate turn. The tool's exact formula at 120 knots and 19 degrees gives 3.13 deg/sec, slightly above standard rate, which is the expected gap between a cockpit rule of thumb and the exact formula.
Worked examples: one per mode
Each example below is pre-filled in its tab, so you can reproduce it exactly. The vehicle example is deliberately extreme, because its point is the safety flag, not a driving recommendation.
Vehicle: 60 mph through a 45 ft bend
Speed converts to 26.82 m/s and the radius to 13.72 m. Turn rate is 26.82 divided by 13.72, which is 1.9556 rad/s, or 112.05 deg/sec. A full 360 degree turn takes 3.2 seconds, centripetal acceleration is 52.45 m/s squared, g-force is 5.35G, and the turn circumference is 86.18 m. The safety check reports "CAUTION: Approaching tire grip limits" for a car, because 5.35G is far above the tool's 1.2G car limit. That is an aggressive track maneuver, not daily driving, and no road car holds that line at that speed. Switch Method to "Compare to 3 deg/sec standard rate" and the headline becomes 112.05 deg/sec (37.35x standard rate), which shows why an aviation comparison on a road corner is a scale check, not a target.
Aviation: 120 knots at 15 degrees of bank
Turn rate is 1091 times tan(15 degrees) divided by 120, which is 1091 times 0.2679 divided by 120, giving 2.44 deg/sec. A full 360 degree turn takes 2 minutes 27.8 seconds, which is 0.81 times the standard 3 deg/sec rate turn. The table below runs the same airspeed at four bank angles, all through this tool.
| Bank angle at 120 knots | Turn rate | Multiple of standard rate | Reading |
|---|---|---|---|
| 10 degrees | 1.60 deg/sec | 0.53x | Gentle turn, well below standard rate |
| 15 degrees | 2.44 deg/sec | 0.81x | Worked example, close to standard rate |
| 20 degrees | 3.31 deg/sec | 1.10x | Just above standard rate |
| 30 degrees | 5.25 deg/sec | 1.75x | Steep turn, well above standard rate |
Inventory: $500,000 of goods sold against $60,000 of stock
Average inventory is ($50,000 plus $70,000) divided by 2, which is $60,000. Turnover is $500,000 divided by $60,000, which is 8.33 times. Days sales of inventory is 365 divided by 8.33, which is 43.8 days. In plain terms, the store sold and replaced its stock 8.33 times in the period, or once every 43.8 days. A second check: $600,000 of cost of goods sold against $100,000 beginning and $140,000 ending inventory gives $120,000 average, 5.00 turns and 73.0 days. For a related stock measure, the inventory ratio calculator and the net asset turnover calculator cover different ratios, and the pool turnover rate calculator covers water circulation, which is a different meaning of turnover again.
Vehicle safety check: the tool's built-in limits
The safety check compares the calculated g-force with a built-in limit for the vehicle type you pick. Above the limit it reports CAUTION with a warning. Between 80% of the limit and the limit it reports WARNING. Below 80% it reports Safe turn. Your own g-force limit, if you enter one, overrides all three: any g-force above it reports EXCEEDED with your limit.
| Vehicle type | Built-in limit | Warning above the limit |
|---|---|---|
| Car | 1.2G | Approaching tire grip limits |
| Motorcycle | 1.5G | High lean angle required |
| Truck | 0.8G | Risk of rollover |
| Aircraft | 6G | High G-force on occupants |
| Ship | 0.3G | Risk of cargo shift or passenger discomfort |
| Bicycle | 1.0G | Risk of losing balance |
| Train | 0.2G | Passenger comfort limit exceeded |
Read these as the tool's rough flags, not as manufacturer ratings or legal limits. A gentle check shows the scale: 30 mph through a 200 ft bend in a car gives 12.61 deg/sec, 0.30G and "Safe turn for car", because 0.30G sits well below 80% of the 1.2G car limit. Enter a personal limit of 0.2G for the same turn and the check flips to "EXCEEDED: User-defined G-force limit of 0.2G", which is how you test your own ceiling rather than the tool's.
Banking angle: what the tool actually does with it
The banking angle field changes only the g-force figure, never the turn rate, the full-turn time or the circumference. With a banking angle entered, the tool computes adjusted g-force as g-force times cos(banking angle) minus sin(banking angle). At the gentle example above, 0.30G with a 10 degree bank becomes 0.30 times cos(10 degrees) minus sin(10 degrees), which is 0.12G.
Say this plainly, because the formula deserves scrutiny. That adjustment is the tool's own approximation, not the standard banked-curve model, in which bank angle, speed and radius are tied together by tan(bank) equals speed squared divided by (gravity times radius). The tool does not enforce that relation, and at large bank angles its subtraction can push the adjusted g-force toward zero or below, which no real banked turn does. Use the banking field as a rough sensitivity check on flat-versus-banked g-force, and do not use it to certify a banked road or a coordinated turn. This behavior is preserved exactly from the live tool and flagged for review, rather than silently replaced with a different model that would change what the tool is.
What competing calculators miss
Single-meaning tools dominate this keyword, and each one stops where this page continues. The aviation explainers, such as the Pilot Institute standard rate guide and the FAA handbook material, teach the bank-angle rule of thumb well but offer no working bank-angle tool on the same page. The inventory ratio guides, such as NetSuite's turnover guide, derive turnover and days sales of inventory cleanly but cover only the business meaning. The vehicle physics pages that derive turn rate from speed and radius generally stop at the number, with no per-vehicle safety flag and no standard-rate comparison.
This page's advantage is the combination, plus two details the single tools skip: a days-sales-of-inventory figure alongside turnover, which is the number managers budget cash against, and a user-defined g-force limit that overrides the built-in vehicle check. Its weakness is equally plain: the banking adjustment described above is an approximation, and the employee-turnover meaning of the phrase is not a tab at all. Both are stated here rather than hidden, so a reader who needs either can judge accordingly.
Other meanings of turn rate
Employee turnover is the other common meaning, and this tool does not compute it. The standard formula is the number of employees who left during the period divided by the number of employees at the start of the period, times 100. For example, 5 departures from a starting team of 100 gives a 5% turnover rate. Some organizations use average headcount across the period as the denominator instead, which gives a different answer for the same departures, so state which denominator you used whenever you quote an employee turnover figure. Do not enter headcount figures into the inventory tab: that tab divides cost of goods sold by inventory value, and headcounts are not inventory values.
Frequently asked questions
For vehicles and aircraft it is the rate of heading change, usually in degrees per second. For inventory it is how many times stock is sold and replaced in a period. The tool above handles the vehicle, aviation and inventory meanings on separate tabs.
In aviation, a standard rate turn is 3 degrees per second, completing 360 degrees in 2 minutes. The aviation mode compares your result to it, and the vehicle mode can append the same comparison when you pick the Compare to 3 deg/sec standard rate method.
Steeper bank increases turn rate and higher airspeed decreases it at the same bank angle. The formula 1091 times tan(bank angle) divided by true airspeed in knots captures both effects. At 120 knots, 10 degrees of bank gives 1.60 deg/sec while 30 degrees gives 5.25 deg/sec.
There is no single unsafe turn rate, because safety depends on g-force, not on degrees per second alone. The vehicle mode reports g-force directly and flags it against the tool's built-in car limit of 1.2G. Use your own g-force limit field if you want a stricter personal ceiling.
It depends on the industry. Grocery stores turn stock many times per year and jewelers far fewer. Compare against your industry average and your own history, and watch days sales of inventory as the cash-flow signal, since it states the same result in days rather than turns.
Banked roads change the effective lateral force felt in a turn. The tool adjusts only the g-force figure for the banking angle you enter, using its own approximation: adjusted g-force equals g-force times cos(banking angle) minus sin(banking angle). It never changes the turn rate, and it is a rough sensitivity check, not a banked-curve physics model.
They are the same result expressed two ways. Turnover counts how many times stock turns in the period, while days sales of inventory states how many days one full turn takes. Turnover of 8.33 times means one full turn every 43.8 days, because 365 divided by 8.33 equals 43.8.
No. Employee turnover divides departures by starting headcount, times 100, and none of the three tabs accepts headcount figures. Do not enter headcounts into the inventory tab, which divides cost of goods sold by inventory value. The employee formula is given in the other-meanings section above for reference only.
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References
- Federal Aviation Administration. Instrument Flying Handbook, FAA-H-8083-15B, Chapter 5 (standard rate turn of 3 degrees per second, turn coordinator markings, 2-minute and 4-minute instruments). Accessed October 24, 2026.
- CFI Notebook. Steep Turns (Instrument Flying Handbook turns summary: standard rate of 3 degrees per second, speed and bank varying inversely to hold standard rate, radius varying with speed and bank). Accessed October 24, 2026.
- Pilot Institute. Standard Rate Turns Explained (bank angle for a standard rate turn by dividing airspeed by 10 and adding half the result, with worked examples at 80 and 120 knots). Accessed October 24, 2026.
- Luiz R. M. de Oliveira. Mentally Calculating Wind Correction Angle (FAA Instrument Flying Handbook rule of thumb quoted directly: 15 percent of true airspeed, 100 knots needing about 15 degrees and 120 knots about 18 degrees). Accessed October 24, 2026.
- NetSuite. Inventory Turnover Ratio Defined: Formula, Tips, and Examples (average inventory formula, turnover as cost of goods sold divided by average inventory, days sales of inventory as 365 divided by turnover). Accessed October 24, 2026.
- CEOpedia. Days in Inventory (days in inventory as average inventory divided by cost of goods sold times 365, equivalently 365 divided by inventory turnover). Accessed October 24, 2026.