Balloon arch calculator
How many balloons a balloon arch needs, how many bags to order, how long it takes to build — and what to charge for it. Enter the width and height, pick a style, change anything.
Example: a 10 ft wide × 8 ft tall organic arch. Densities, prices and times are starting points — replace them with your own.
1 · Arch size
Length along the arch: 20.7 ft (half an ellipse, 10 × 8 ft) · 6.3 m
2 · Style & balloons
3 · Time, frame & price
From arch size to balloons and price
Balloons follow the length of the arch measured along the curve, so the first step is turning width and height into that length.
- Semicircle (as tall as half its width): length = π × width ÷ 2. An 8 ft wide semicircle is 3.1416 × 8 ÷ 2 ≈ 12.6 ft.
- Width × height: the arch is treated as half an ellipse, half as wide as the arch on one side (a = width ÷ 2) and as tall as the arch (b = height). Its length uses Ramanujan’s approximation: π × [3(a + b) − √((3a + b)(a + 3b))] ÷ 2. For a 10 ft × 8 ft arch, a = 5 and b = 8, which gives about 20.7 ft. The approximation is within a fraction of a percent of the exact length for arch shapes.
- Measured length: if you have the frame, tape along it from floor to floor — that beats any formula.
- Balloons per size = density per foot × length (metres × 3.28 to feet), plus your spares %, rounded up. Bags assume 100 per bag for 5″ and 11″ and 25 per bag for 18″ and 24″.
- Cost = balloons used × (bag price ÷ balloons per bag) + strip and glue dots per foot + frame wear (frame price ÷ jobs you expect from it) + hours × hourly rate + travel. Hours = build time per foot × length + frame setup, install and takedown.
- Price = cost ÷ (1 − target margin), rounded up to your step. Per foot or metre = price ÷ length along the arch.
Balloons for common arch sizes
Estimates including 10% spares, using the example densities below. Your own recipe may be denser or lighter.
| Arch | Along the curve | Organic full | Organic airy | Classic 11″ clusters |
|---|---|---|---|---|
| 6 ft wide semicircle (1.8 m) | 9.4 ft · 2.9 m | 157 | 102 | 104 |
| 8 ft wide semicircle (2.4 m) | 12.6 ft · 3.8 m | 208 | 136 | 139 |
| 8 ft wide × 7 ft tall (2.4 m) | 17.6 ft · 5.4 m | 292 | 189 | 194 |
| 10 ft wide × 8 ft tall (3 m) | 20.7 ft · 6.3 m | 343 | 222 | 228 |
| 12 ft wide × 9 ft tall (3.7 m) | 23.8 ft · 7.3 m | 395 | 255 | 262 |
The assumptions, in plain sight
An arch is a garland on a frame, so the starting densities are the same ones our balloon garland calculator uses — balloons per foot of finished arch:
| Style | Size mix | 5″ | 11″ | 18″ | 24″ | Build time / ft |
|---|---|---|---|---|---|---|
| Classic | 11″ quad clusters | – | 10 | – | – | 15 min |
| Classic | 5″ quad clusters (mini) | 20 | – | – | – | 15 min |
| Classic | 11″ clusters + 5″ accents | 8 | 10 | – | – | 15 min |
| Organic full | Balanced 5″ / 11″ / 18″ | 6 | 8 | 1 | – | 18 min |
| Organic full | Big & bold with 24″ | 6 | 7 | 1.5 | 0.5 | 18 min |
| Organic full | Petite 5″ / 11″ | 8 | 9 | – | – | 18 min |
| Organic airy | Balanced 5″ / 11″ / 18″ | 4 | 5 | 0.7 | – | 12 min |
| Organic airy | Big & bold with 24″ | 3 | 4 | 1 | 0.4 | 12 min |
| Organic airy | Petite 5″ / 11″ | 5 | 6 | – | – | 12 min |
| Example input | Starting value |
|---|---|
| Bag prices (professional latex) | $10 per 100 × 5″ · $17 per 100 × 11″ · $23.50 per 25 × 18″ · $47.50 per 25 × 24″ |
| Spares and pops | 10% |
| Strip, glue dots and ties | $0.16 per foot |
| Frame or stand | $150, spread over 20 jobs |
| Frame setup, install and takedown | 1.5 hours |
| Hourly rate · travel | $25 an hour · $25 per job |
| Target margin | 60%, price rounded up to the nearest $5 |
These are typical US reference prices used as a starting point, not market data — your supplier, colours, region and speed will differ, so replace each one. Switching currency rescales the examples roughly until you type your own. Foils, signage, greenery and helium are not included: price the whole job in the balloon pricing calculator or check what you keep with the event profit calculator. For a per-foot rate that holds up, read balloon garland price per foot and how to price a balloon garland, and take a deposit that covers your balloons — see event deposits: how much and when.
Running a balloon business? Sarvyam for balloon decorators keeps your arch recipes, counts balloons on every quote and collects deposits — see plans and pricing.
Questions, answered
How many balloons do I need for a balloon arch?
It depends on the length along the curve, not the width. A 10 ft wide × 8 ft tall arch is about 20.7 ft along the curve; at a full organic density of about 15 balloons per foot that is roughly 343 balloons with 10% spares (137 × 5″, 183 × 11″ and 23 × 18″). An airy organic or classic quad-cluster arch of the same size uses fewer. Treat these as starting points and adjust the densities to match your own builds.
How many balloons for an 8 ft balloon arch?
An 8 ft wide semicircle arch is about 12.6 ft along the curve (π × 8 ÷ 2). As a full organic arch that is around 208 balloons including 10% spares; a classic arch in 11″ quad clusters needs about 139. If your arch is taller than it is wide, choose “Width × height” — the extra height adds length and balloons.
How do I measure a balloon arch?
Measure the width from the outside of one leg to the outside of the other, and the height from the floor to the top of the arch. If you already have a frame, the most accurate way is to run a tape measure along it from floor to floor and use “Measured length”. Balloon counts, build time and price per foot all follow the length along the curve.
How much should I charge for a balloon arch?
Price it from your own costs: balloons with spares, strip and glue dots, wear on your frame, your hours at a fair rate and travel, then divide by (1 − your target margin). With the example numbers on this page — a 10 ft × 8 ft full organic arch, US reference balloon prices, $25 an hour and a 60% margin — that comes to about $740 (around $36 per foot of arch). Your build speed and hourly rate move the price more than the balloons do.
How long does it take to build a balloon arch?
The calculator assumes about 18 minutes per foot for a full organic arch, 12 for an airy one and 15 for classic clusters, plus time to set up the frame, install and take down. Many decorators pre-build sections at the studio and attach them on site. Time a few of your own builds and use those numbers.
Should I charge per foot for a balloon arch?
Per-foot pricing is easy to explain and scales from a small doorway arch to a stage arch, but quote the length along the curve, not the width — an 8 ft wide arch is closer to 13 ft of balloons. Add delivery, foils, signage and greenery on top, and set a minimum so small arches still cover your travel and setup.
Why does the calculator need the height as well as the width?
Two arches of the same width can need very different numbers of balloons. A tall arch (10 ft wide × 8 ft tall) is about 21 ft along the curve, while a round semicircle of the same width (5 ft tall) is under 16 ft. The calculator treats the arch as half an ellipse and works out its length for you.
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