Tools · Comparison
Best Air Rifle FPE Calculators Compared (2026)
Researched by James · Updated · Editorial policy
On this page
- What is the best FPE calculator for air rifles?
- How do the FPE calculators and ballistics apps compare?
- Which calculator is best for each job?
- How fair is this site's own FPE calculator?
- How do you check any FPE calculator by hand?
- What about trajectory and holdover?
- Which calculators were left out, and why?
- Does a calculator need a chronograph?
- FAQ
- Sources
Each tool below was checked on its own page or App Store listing in October 2026. I did not run side-by-side tests, and prices change. The site's own calculator is flagged as such; it is judged against the others on what each page shows. Full methodology & editorial policy →
What is the best FPE calculator for air rifles?
The best one is the simplest tool that does your job. If you only need to turn pellet weight and chronographed speed into energy, a free web calculator wins on speed and cost. If you need to know where the pellet lands at 40 yards, no FPE calculator can help, and a ballistics app is the right tool. Most hunters need both: an FPE check once per load (see air rifle FPE for hunting) and a holdover chart if they shoot past their zero.
How do the FPE calculators and ballistics apps compare?
Four tools passed the "confirmed to exist and open now" test. They split cleanly into energy calculators and a ballistics app.
| Tool | Platform and price | What it takes in | Units and joules | Trajectory? | Best for |
|---|---|---|---|---|---|
| FPE Calculator (this site's: James Southern Outdoors) | Any browser; free | Weight and speed, or a target energy to find the speed needed | Grains or grams; fps or m/s; FPE and joules | No | Energy and legal-limit checks |
| Airgun Depot calculators | Any browser; free | Four tools: FPE (grains, fps), FPS (energy, grains), ballistic coefficient (two ranges and speeds), retained velocity (muzzle speed, range, BC) | Grains, fps, yards; FPE and joules out; no unit switch | Retained speed only; no drop | Energy plus a quick retained-speed estimate |
| Omni Calculator FPE | Any browser; free | Weight and speed; also works backward | Grains and fps; foot-pounds only | No | A generic backup, not airgun-specific |
| ChairGun Elite Ballistic Tool+ and Ballistic Tool (Ballistic Solutions LLC) | App Store: iPhone, iPad, Mac. Tool+ is free with a PRO subscription ($9.99 a year on the listing); the Ballistic Tool is a one-time purchase | Weight, BC with a choice of drag models, speed, scope and weather; about 500 air rifle pellets in its database | Several unit systems; plots energy, but the listing doesn't say in which units | Yes: drop, wind, holdover, with about 2,600 reticles | Holdover and trajectory |
Sources: each tool's own page or App Store listing (see Sources and the links below). The Omni Calculator divisor is 450,240; this site's is 450,436. ChairGun Elite's listing shows two versions; I could not confirm an Android app.
Which calculator is best for each job?
| Your job | Use | Why |
|---|---|---|
| Quick energy check | This site's FPE calculator or Airgun Depot's | Both take grains and fps and return FPE and joules in one step. Ours also takes grams and m/s |
| Legal-limit check | This site's FPE calculator | It flags the UK 12 ft-lb and Germany 7.5 J limits; none of the other pages I opened show legal flags |
| Holdover and trajectory | ChairGun Elite | It is the only tool here that models drop, wind and reticles. This site's calculator does not do trajectory at all |
| Energy kept at range | Airgun Depot's retained-velocity tool, or ChairGun's energy chart | Airgun Depot gives speed at range from a BC, which you then convert to FPE; ChairGun plots energy over distance |
| Phone in the field | ChairGun Elite on iPhone; any web calculator in the phone browser | I couldn't confirm an Android ballistics app with airgun support, so Android users get the web tools |
Verdict: use a web calculator for energy and a ballistics app for holdover. Don't expect one tool to be best at both.
How fair is this site's own FPE calculator?
This site's calculator is good at energy and honest about its limits. It was built for the FPE questions this site's guides keep asking, and it stops there.
What it does well
- FPE and joules from grains or grams and fps or m/s
- "Speed for an energy" mode: the fps a target energy needs
- UK 12 ft-lb and Germany 7.5 J flags, plus a velocity table and share links
Where it stops
- No trajectory, drop or holdover; use a ballistics app
- No ballistic coefficient or retained-energy estimate; Airgun Depot's retained-velocity tool covers that
- No pellet database; you enter the weight yourself
The legal flags are a convenience, not legal advice. Laws change and differ by country, region and city.
How do you check any FPE calculator by hand?
Square the speed, multiply by the weight in grains, and divide by 450,436. Take an 18.13 grain .22 pellet at 880 fps: 880² = 774,400; × 18.13 = 14,039,872; ÷ 450,436 = 31.2 FPE. Multiply by 1.3558 for 42.3 joules.
The metric route should agree. 18.13 grains is 1.175 grams and 880 fps is 268.2 m/s, so ½ × 0.001175 kg × 268.2² = 42.3 J. Run it backward for the speed a 12 FPE floor needs: √(12 × 450,436 ÷ 18.13) = 546 fps.
If a calculator disagrees by more than a tenth of a foot-pound, check the units first. The divisor only matters in the fourth digit: 450,240 gives 32.62 FPE for 18.13 grains at 900 fps and 450,436 gives 32.60. Pyramyd AIR's muzzle energy page uses 450,240 and a rule of thumb worth knowing: at 671 fps, foot-pounds equal grains. For more on what the number means, see the FPS vs FPE explainer and the airgun FPE chart.
What about trajectory and holdover?
Trajectory needs a ballistic coefficient, and the drag model matters. Hard Air Magazine says it calculates pellet BCs with the GA drag model and slug BCs with G1. ChairGun Elite's listing lists GA and G1 among its drag models, so it can use those published numbers in the model they were measured in. The step-by-step holdover method is in the mil-dot holdover guide.
Which calculators were left out, and why?
I left out anything I couldn't confirm for airguns today. Here is the list, so you can check for yourself:
- Strelok Pro. Hawke's end-of-life page names it as Hawke's favorite replacement for ChairGun. But two regional App Store pages for the original listing (Igor Borisov) returned "not found" when I tried them, and the current App Store listing under the Strelok name (Strelok Pro-Ballistic Platform, Strelok LLC) never mentions airguns or pellets. I couldn't tell if it's the same product, so check before paying.
- Hawke ChairGun Pro and X-Act. Hawke ended support at the end of 2018. ChairGun Elite is listed under Ballistic Solutions LLC, not Hawke, and Hawke's page doesn't mention it.
- Applied Ballistics and Kestrel. I found no documentation of airgun pellet support.
- Gamo, Crosman, Umarex and Pyramyd AIR. I found no interactive calculators. Umarex and Pyramyd AIR publish explainers with the formula, but I couldn't confirm a tool on Pyramyd's page.
- Hard Air Magazine. It publishes measured ballistic coefficients rather than a calculator I could find.
Does a calculator need a chronograph?
Yes, for a number you can trust. A calculator multiplies what you enter, and the speed on the box usually comes from a light alloy pellet. Chronograph the load you hunt with and enter the average of a ten-shot string. The Garmin Xero C1 Pro's manual has an air rifle mode and calculates energy when you enter the projectile weight, which makes a handy cross-check. Options are in the best airgun chronographs guide.
To feed a calculator real numbers
As an Amazon Associate, James Southern Outdoors earns from qualifying purchases. Some links may earn a commission at no cost to you. Prices and availability change. Retailer never decides the recommendation.
Verdict
Use this site's or Airgun Depot's calculator to check energy and joules, add ChairGun Elite if you have an iPhone, iPad or Mac and need holdover, and verify any other app's airgun support yourself before you pay. Whatever you use, test it once with the worked example above.
FAQ
What is the best FPE calculator for air rifles?
For a quick energy check, any free web calculator that takes grains and fps works: this site's FPE calculator and Airgun Depot's both return foot-pounds and joules. For drop and holdover you need a ballistics app, and ChairGun Elite is the one with a confirmed airgun pellet database. Pair a calculator with a chronograph for real numbers.
Is there a free FPE calculator that shows joules?
Yes. This site's FPE calculator and Airgun Depot's FPE calculator both show foot-pounds and joules, and this site's also accepts grams and m/s and works backward from a target energy. Omni Calculator's FPE tool returns foot-pounds only.
Why do FPE calculators give slightly different answers?
Mostly the divisor and the units. This site uses 450,436; Pyramyd AIR, Omni Calculator and Air Arms print 450,240. For 18.13 grains at 900 fps that's 32.60 vs 32.62 FPE, a 0.04% gap. A larger difference means a unit mix-up, such as grams for grains or m/s for fps.
Can an FPE calculator tell me bullet drop at 40 yards?
No. An FPE calculator needs only weight and speed and returns energy. Drop depends on the ballistic coefficient, scope height and zero, so it takes a ballistics app. Airgun Depot's retained-velocity tool gets as far as speed at range, not drop.
Is there an app that calculates airgun trajectory?
ChairGun Elite Ballistic Tool+ and Ballistic Tool, listed on the App Store under Ballistic Solutions LLC for iPhone, iPad and Mac, calculate trajectory and holdover and include about 500 air rifle pellets. I could not confirm an Android version, or that other popular ballistics apps support airguns today.
Is ChairGun still a Hawke product?
Hawke's end-of-life page says it ended support for its ChairGun and X-Act software at the end of 2018 and doesn't mention ChairGun Elite. The App Store lists ChairGun Elite under Ballistic Solutions LLC, so don't assume the two are the same product.
Do I need a chronograph to use an FPE calculator?
For a real number, yes. A calculator only multiplies what you enter, and the speed on the box is rarely the speed of your hunting pellet. Some chronographs, such as the Garmin Xero C1 Pro, calculate energy themselves once you enter the projectile weight.
How do I convert FPE to joules?
Multiply foot-pounds by 1.3558. For example 31.2 FPE is 42.3 J, and 12 FPE is 16.27 J. Divide joules by 1.3558 to go back.
Sources
- Airgun Depot — Airgun calculators (FPE, FPS, ballistic coefficient, retained velocity)
- App Store — ChairGun Elite Ballistic Tool+ (Ballistic Solutions LLC)
- App Store — ChairGun Elite Ballistic Tool (one-time purchase listing)
- Hawke Optics US — ChairGun and X-Act end of life
- Pyramyd AIR — Muzzle energy explanation and definition
- Hard Air Magazine — New ballistic coefficients for JSB slugs, Hades pellets and more (drag models)
